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{{Short description|Class of arthropods}} | |||
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{{Use dmy dates|date=January 2015}} | {{Use dmy dates|date=January 2015}} | ||
{{Automatic taxobox | {{Automatic taxobox | ||
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|fossil_range = {{fossilrange|Carboniferous|Present|earliest=400}} | ||
|image = Insects - Neoptera - Paleoptera - Apterygota.jpg<!--See talk page before editing--> | |||
| image = Insect collage.png | |||
|image_caption = Insects have a three-part body: head with large ]s and ], a ] with three pairs of legs, and a segmented abdomen. Many groups also have two pairs of wings. | |||
| image_caption = Clockwise from top left: dance fly ('']''), long-nosed weevil ('']''), mole cricket ('']''), ] (''Vespula germanica''), emperor gum moth ('']''), assassin bug (]) | |||
|display_parents = 2 | |||
| image2 = A Magicicada chorus containing M. septendecim, M. cassini, and M. septendecula - pone.0000892.s004.oga | |||
|taxon = Insecta | |||
| image2_caption = A chorus of several '']'' species | |||
|authority = ], ] | |||
| display_parents = 2 | |||
|subdivision_ranks = Subgroups | |||
| taxon = Insecta | |||
|subdivision = * ] | |||
| authority = ], ] | |||
* ] | |||
| subdivision_ranks = Subgroups | |||
** ] | |||
| subdivision = ]. | |||
** ] | |||
| synonyms = | |||
* Ectognatha | |synonyms = * Ectognatha | ||
* Entomida | * Entomida | ||
}} | }} | ||
] climbs wind blown grass and flies off.]] | |||
'''Insects''' (from ] ''{{lang|la|insectum}}'') are ] ]s of the ] '''Insecta'''. They are the largest group within the ] ]. Insects have a ]ous ], a three-part body (], ] and ]), three pairs of jointed ], ]s, and a pair of ]. Insects are the most diverse group of animals, with more than a million described ]; they represent more than half of all animal species. | |||
'''Insects''' or '''Insecta''' (from ] ''{{lang|la|insectum}}'') are ] ]s and the largest group within the ] ]. Definitions and ] vary; usually, insects comprise a class within the Arthropoda. As used here, the term Insecta is ] with '''Ectognatha'''. Insects have a ]ous ], a three-part body (], ] and ]), three pairs of jointed ], ]s and one pair of ]. Insects are the most diverse group of animals; they include more than a million described ] and represent more than half of all known living ]s.<ref name="Chapman">{{cite book |author1 =Chapman, A.D. |year=2006 |title=Numbers of living species in Australia and the World |publisher=Canberra: ] |isbn=978-0-642-56850-2 |url=http://www.deh.gov.au/biodiversity/abrs/publications/other/species-numbers/index.html}}</ref><ref>{{cite web|url=http://www.globalchange.umich.edu/globalchange2/current/lectures/biodiversity/biodiversity.html|archiveurl=https://web.archive.org/web/20150220154543/http://www.globalchange.umich.edu/globalchange2/current/lectures/biodiversity/biodiversity.html |archivedate=20 February 2015 |title=Threats to Global Diversity|last=Wilson|first=E.O. |accessdate=17 May 2009}}</ref> The total number of ] species is estimated at between six and ten million;<ref name="Chapman" /><ref>{{cite journal |author1=Novotny, Vojtech |author2=Basset, Yves |author3=Miller, Scott E. |author4=Weiblen, George D. |author5=Bremer, Birgitta |author6=Cizek, Lukas |author7=Drozd, Pavel |year=2002 |title=Low host specificity of herbivorous insects in a tropical forest |journal=] |pmid=11976681 |volume=416 |issue=6883 |pages=841–844 |doi=10.1038/416841a|bibcode = 2002Natur.416..841N}}</ref><ref name="number">{{cite book|author=Erwin, Terry L. |year=1997 |title=Biodiversity at its utmost: Tropical Forest Beetles |pages=27–40|url=http://entomology.si.edu/StaffPages/Erwin/T's%20updated%20pub%20PDFs%2010Jan2014/121_1995_Biodiversity-at-its-utmost.pdf}} In: {{cite book |editor1=Reaka-Kudla, M.L. |editor2=Wilson, D.E. |editor3=Wilson, E.O. |title=Biodiversity II |publisher=Joseph Henry Press, Washington, D.C.}}</ref> potentially over 90% of the animal life forms on Earth are insects.<ref name="number"/><ref>{{cite journal|last=Erwin|first=Terry L.|year=1982|title=Tropical forests: their richness in Coleoptera and other arthropod species|journal=The Coleopterists Bulletin |volume=36|pages=74–75|url=https://repository.si.edu/bitstream/handle/10088/4383/Classic_papers_in_Foundations.pdf?sequence=1&isAllowed=y}}</ref> Insects may be found in nearly all ], although only a small number of species reside in the oceans, which are dominated by another arthropod group, ]s. | |||
The insect ] consists of a ] and a ]. Most insects reproduce ]. Insects ] through a system of ] along their sides, connected to ] that take air directly to the tissues. The blood therefore does not carry oxygen; it is only partly contained in vessels, and some circulates in an open ]. Insect vision is mainly through their ]s, with additional small ]. Many insects can hear, using ]s, which may be on the legs or other parts of the body. Their ] is via receptors, usually on the antennae and the mouthparts. | |||
Nearly all insects hatch from ]s. Insect growth is constrained by the inelastic ] and development involves a series of ]. The immature stages often differ from the adults in structure, habit and habitat, and can include a passive ]l stage in those groups that undergo ]. Insects that undergo ] lack a pupal stage and adults develop through a series of ] stages.<ref name="mcgraw-hill">"insect physiology" ''McGraw-Hill Encyclopedia of Science and Technology'', Ch. 9, p. 233, 2007</ref> The higher level relationship of the ] is unclear. Fossilized insects of enormous size have been found from the ] Era, including ] with wingspans of 55 to 70 cm (22 to 28 in). The most diverse insect groups appear to have ] with ]. | |||
Nearly all insects hatch from ]s. Insect growth is constrained by the inelastic exoskeleton, so development involves a series of ]. The immature stages often differ from the adults in structure, habit and habitat. Groups that undergo ] often have a nearly immobile ]. Insects that undergo ] lack a pupa, developing through a series of increasingly adult-like ] stages. The higher level relationship of the ] is unclear. Fossilized insects of enormous size have been found from the ] Era, including ] with wingspans of {{convert|55|to|70|cm|in|abbr=on}}. The most diverse insect groups appear to have ] with ]s. | |||
Adult insects typically move about by walking, flying, or sometimes swimming. As it allows for rapid yet stable movement, many insects adopt a tripedal gait in which they walk with their legs touching the ground in alternating triangles, composed of the front & rear on one side with the middle on the other side. Insects are the only invertebrates to have evolved flight, and all flying insects derive from one common ancestor. Many insects spend at least part of their lives under water, with ] adaptations that include ]s, and some adult insects are aquatic and have adaptations for swimming. Some species, such as ], are capable of walking on the surface of water. Insects are mostly solitary, but some, such as certain ]s, ]s and ]s, are social and live in large, well-organized colonies. Some insects, such as ]s, show maternal care, guarding their eggs and young. Insects can communicate with each other in a variety of ways. Male ]s can sense the ]s of female moths over great distances. Other species communicate with sounds: ] ], or rub their wings together, to attract a mate and repel other males. ] ]s communicate with light. | |||
Adult insects typically move about by walking and flying; some can swim. Insects are the only invertebrates that can achieve sustained powered flight; ] evolved just once. Many insects are at least partly ], and have ]e with gills; in some species, the adults too are aquatic. Some species, such as ], can walk on the surface of water. Insects are mostly solitary, but some, such as ]s, ]s and ]s, are ] and live in large, well-organized ]. Others, such as ]s, provide maternal care, guarding their eggs and young. Insects can communicate with each other in a variety of ways. Male ]s can sense the ]s of female moths over great distances. Other species communicate with sounds: ] ], or rub their wings together, to attract a mate and repel other males. ] ]s communicate with light. | |||
Humans regard certain insects as ], and attempt to control them using ]s, and a host of other techniques. Some insects damage crops by feeding on sap, leaves, fruits, or wood. Some species are ], and may ] diseases. Some insects perform complex ecological roles; ], for example, help consume ] but also spread diseases. Insect ] are essential to the life cycle of many flowering plant species on which most organisms, including humans, are at least partly dependent; without them, the terrestrial portion of the biosphere would be devastated.<ref>{{cite encyclopedia |url=http://www.britannica.com/EBchecked/topic/289001/insect |author=Vincent Brian Wigglesworth |title=Insect |work=] online |accessdate=19 April 2012}}</ref> Many insects are considered ecologically beneficial as predators and a few provide direct economic benefit. ]s produce ] and honey bees produce ] and both have been domesticated by humans. Insects are consumed as food in 80% of the world's nations, by people in roughly 3000 ethnic groups.<ref name="theguardian">Damian Carrington. "", '']'' 1 August 2010. Retrieved 27 February 2011.</ref><ref name="Ramos-Elorduy 1998 44">{{cite book |title=Creepy crawly cuisine: the gourmet guide to edible insects |last=Ramos-Elorduy |first=Julieta |author2=Menzel, Peter |year=1998 |publisher=Inner Traditions / Bear & Company |isbn=978-0-89281-747-4 |page=44 |url=https://books.google.com/?id=Q7f1LkFz11gC |accessdate=23 April 2014}}</ref> | |||
Humans regard many insects as ], especially those that damage crops, and attempt to control them using ]s and other techniques. Others are ], and may act as ] of ]. Insect ] are essential to the reproduction of many flowering plants and so to their ecosystems. Many insects are ecologically beneficial as predators of pest insects, while a few provide direct economic benefit. Two species in particular are economically important and were domesticated many centuries ago: ]s for ] and ]s for ]. Insects are consumed as food in 80% of the world's nations, by people in roughly 3,000 ethnic groups. Human activities are having serious effects on ]. | |||
== Etymology == | == Etymology == | ||
The word "insect" comes from the ] word ''{{lang|la|]}}'', meaning "with a notched or divided body", or literally "cut into", from the neuter singular perfect passive participle of {{lang|la|]}}, "to cut into, to cut up", from ''in''- "into" and ''secare'' "to cut";<ref name="etymonline">{{cite web | url = http://www.etymonline.com/index.php?term=insect&allowed_in_frame=0 | title = Online Etymological Dictionary | last=Harper |first=Douglas |author2=Dan McCormack |date=November 2001|publisher=LogoBee.com |page=1 |accessdate=1 November 2011}} | |||
</ref> because insects appear "cut into" three sections. A ] of ] {{lang|el|ἔντομον}} , "cut into sections", ] introduced the Latin designation as a loan-translation of the ] word {{lang|el|]}} (''éntomos'') or "insect" (as in ]), which was ]'s term for this class of life, also in reference to their "notched" bodies. "Insect" first appears documented in English in 1601 in ]'s translation of Pliny. Translations of Aristotle's term also form the usual word for "insect" in ] ({{lang|cy|]}}, from ''{{lang|cy|]}}'' "to cut" and '' mil'', "animal"), ] (''zareznik'', from ''rezati'', "to cut"), ] ({{lang|ru|]}} ''nasekomoje'', from ''seč'/-sekat''', "to cut"), etc.<ref name="etymonline" /><ref>{{cite web|url=http://www.ezglot.com/words.php?w=insect&l=eng|title=Insect translations}}</ref> | |||
The word ''insect'' comes from the ] word {{lang|la|insectum}}<!--past participle--> from {{lang|la|in}}, "cut up",<ref>{{cite dictionary |url=https://www.perseus.tufts.edu/hopper/text?doc=Perseus%3Atext%3A1999.04.0059%3Aentry%3Dinseco1 |title=insĕco |last1=Lewis |first1=Charlton T. |last2= Short |first2=Charles |dictionary=A Latin Dictionary |publisher=Perseus Digital Library |date=1879 }}</ref> as insects appear to be cut into three parts. The Latin word was introduced by ] who ]d the ] word {{lang|grc|ἔντομον}} ''éntomon'' "insect" (as in ]) from {{lang|grc|]}} ''éntomos'' "cut in pieces";<ref name="Liddell">{{cite web |url=https://www.perseus.tufts.edu/hopper/text?doc=Perseus:text:1999.04.0057:entry=e)/ntomos |title=ἔντομος |last1=Liddell |first1=Henry George |last2=Scott |first2=Robert |work=A Greek-English Lexicon |publisher=Perseus Digital Library |date=1940 }}</ref> this was ]'s term for this ], also in reference to their notched bodies. The English word ''insect'' first appears in 1601 in ]'s translation of Pliny.<ref name="etymonline">{{cite web |url=http://www.etymonline.com/index.php?term=insect&allowed_in_frame=0 |title=Online Etymological Dictionary |last=Harper |first=Douglas |author2=McCormack, Dan |date=November 2001 |publisher=LogoBee.com |page=1 |access-date=1 November 2011 |archive-url=https://web.archive.org/web/20120111164850/http://www.etymonline.com/index.php?term=insect&allowed_in_frame=0 |archive-date=11 January 2012 |url-status=live }}</ref><ref>{{Cite web|url=https://www.ezglot.com/words.php?w=insect&l=eng |title=insect translations |website=ezglot.com}}</ref> | |||
== Definitions == | |||
The precise definition of the taxon Insecta and the equivalent English name "insect" varies; three alternative definitions are shown in the table. | |||
== Insects and other bugs == | |||
{| class="wikitable" | |||
|+ Definition of Insecta | |||
! Group !!colspan=3| Alternative definitions | |||
|- | |||
| ] (springtails) ||rowspan=6|Insecta ''sensu lato''<br>=Hexapoda || rowspan=3|]<br>(paraphyletic) || rowspan=5|]<br>(wingless hexapods)<br>(paraphyletic) | |||
|- | |||
| ] (coneheads) | |||
|- | |||
| ] (two-pronged bristletails) | |||
|- | |||
| ] (jumping bristletails) ||rowspan=3|Insecta ''sensu stricto''<br>=Ectognatha | |||
|- | |||
| ] (silverfish) | |||
|- | |||
| ] (winged insects) ||Insecta ''sensu strictissimo'' | |||
|} | |||
=== Distinguishing features === | |||
In the broadest ], Insecta '']'' consists of all ].<ref name=Sasaki/>{{sfn|Chinery|1993|p=10}} Traditionally, insects defined in this way were divided into "Apterygota" (the first five groups in the table)—the wingless insects—and ]—the winged insects.{{sfn|Chinery|1993|pp=34–35}} However, modern phylogenetic studies have shown that "Apterygota" is not monophyletic,<ref name=Kjer/> and so does not form a good taxon. A narrower circumscription restricts insects to those hexapods with external mouthparts, and comprises only the last three groups in the table. In this sense, Insecta '']'' is equivalent to Ectognatha.<ref name=Sasaki/><ref name=Kjer/> In the narrowest circumscription, insects are restricted to hexapods that are either winged or descended from winged ancestors. Insecta '']'' is then equivalent to Pterygota.<ref name=HughLong16/> For the purposes of this article, the middle definition is used; insects consist of two wingless taxa, ] (jumping bristletails) and ] (silverfish), plus the winged or secondarily wingless Pterygota. | |||
In common speech, insects and other terrestrial ]s are often called '''bugs'''.{{efn|The ] notes that "in everyday conversation", ''bug'' "refers to land arthropods with at least six legs, such as insects, spiders, and centipedes".<ref> at Museum of New Zealand Te Papa Tongarewa website. Accessed 10 March 2022.</ref> In a chapter on "Bugs That Are Not Insects", entomologist Gilbert Walbauer specifies centipedes, millipedes, arachnids (spiders, ], scorpions, ]s, ]s and ticks) as well as the few terrestrial crustaceans (]s and ]s).<ref name="Waldbauer 1998">{{cite book |last=Waldbauer |first=Gilbert |title=The Handy Bug Answer Book |publisher=Visible Ink |year=1998 |url=https://archive.org/details/handybuganswerbo00wald/page/5/mode/2up |pages=1, 5–26 |isbn=9781578590490}}</ref>}} Entomologists to some extent reserve the name "bugs" for a narrow category of "]", insects of the order ], such as ]s and ]s.<ref name="Waldbauer 1998"/> Other terrestrial arthropods, such as ]s, ]s, ], ]s, ]s and ]s, are sometimes confused with insects, since they have a jointed exoskeleton.<ref name="Chinery intro 1993">{{cite book |last=Chinery |first=Michael |date=1993 |chapter=Introduction |title=Insects of Britain & Northern Europe |edition=3rd |location=London |publisher=HarperCollins |isbn=978-0-00-219918-6 |pages=11–13}}</ref> Adult insects are the only arthropods that ever have wings, with up to two pairs on the thorax. Whether winged or not, adult insects can be distinguished by their three-part body plan, with head, thorax, and abdomen; they have three pairs of legs on the thorax.{{sfn|Gullan|Cranston|2005|pp=22–48}} | |||
<gallery class=center mode=nolines widths=175 heights=175 caption="Insects and other bugs that could be confused with them"> | |||
File:Gemeine Heidelibelle (Sympetrum vulgatum) 4 (cropped).jpg|'''Insect'''<!--indicating THIS group-->: Six legs, three-part body<br/>(head, thorax, abdomen),<br/>up to two pairs of wings | |||
File:Wolfsspinne Trochosa Rose-20190905-RM-081613 (cropped).jpg|]: eight legs,<br/>two-part body | |||
File:Armadillidium_vulgare_001.jpg|]: seven pairs of legs, seven body<!--thoracic, but that's too tech. for this caption--> segments (plus head and tail) | |||
File:Scolopendra viridicornis nigra (cropped).jpg|]: many legs,<br/>one pair per segment | |||
File:Milli's on the back (cropped).jpg|]: many legs,<br/>two pairs per segment | |||
</gallery> | |||
=== Diversity === | |||
{{Main|Insect biodiversity}} | |||
]s are insects (left side of diagram).]] | |||
Estimates of the total number of insect species vary considerably, suggesting that there are perhaps some 5.5 million insect species in existence, of which about one million have been described and named.<ref name="Stork2018">{{cite journal |last=Stork |first=Nigel E. |title=How Many Species of Insects and Other Terrestrial Arthropods Are There on Earth? |journal=Annual Review of Entomology |date=7 January 2018 |volume=63 |issue=1 |pages=31–45 |doi=10.1146/annurev-ento-020117-043348 |pmid=28938083 |s2cid=23755007 |doi-access=free }}</ref> These constitute around half of all ] species, including ]s, ]s, and ].<ref>{{cite journal |last=Erwin |first=Terry L. |year=1982 |title=Tropical forests: their richness in Coleoptera and other arthropod species |journal=The Coleopterists Bulletin |volume=36 |pages=74–75 |url=https://repository.si.edu/bitstream/handle/10088/4383/Classic_papers_in_Foundations.pdf?sequence=1&isAllowed=y |access-date=16 September 2018 |archive-url=https://web.archive.org/web/20150923014947/https://repository.si.edu/bitstream/handle/10088/4383/Classic_papers_in_Foundations.pdf?sequence=1&isAllowed=y |archive-date=23 September 2015 |url-status=live}}</ref> The most diverse insect ]s are the Hemiptera (true bugs<!--intentional repeat, this is an introductory section-->), Lepidoptera (butterflies and moths), Diptera (true flies), Hymenoptera (wasps, ants, and bees), and Coleoptera (beetles), each with more than 100,000 described species.<ref name="Stork2018"/>{{-}} | |||
<gallery class=center mode=packed widths=150 heights=150 caption="Insects are extremely diverse. Five groups each have over 100,000 described species."> | |||
File:Palomena prasina MHNT Léguevin Blanc.jpg|True bugs<br/>(]) | |||
File:Peacock butterfly (Aglais io) 2.jpg|Butterflies and moths<br/>(]) | |||
File:Asilidae by kadavoor.jpg|Flies<br/>(]) | |||
File:Specimen of Podalonia tydei (Le Guillou, 1841) (cropped).jpg|Wasps<br/>(]) | |||
File:7-Spotted-Ladybug-Coccinella-septempunctata-sq1.jpg|Beetles<br/>(]) | |||
</gallery> | |||
=== Distribution and habitats === | |||
<gallery class=center mode=packed widths=165 heights=165 caption="Insects occur in habitats as varied as snow, freshwater, the tropics, desert, and even the sea."> | |||
File:Boreus hyemalis 5930585 (cropped).jpg|The snow scorpionfly '']'' on snow | |||
File:Dytiscus marginalis larva.jpg|The great diving beetle '']'' larva in a pond | |||
File:Green Orchid Bee (Euglossa dilemma) (7406599274).jpg|The green orchid bee '']'' of Central America | |||
File:SGR laying (cropped).jpg|The desert locust '']'' laying eggs in sand | |||
File:Halobates sp. (Heteroptera Gerridae), 20 August 2011, Castle Beach, Kailua (Oahu), Hawaii03 (cropped).jpg|Sea skater '']'' on a Hawaii beach | |||
</gallery> | |||
Insects are distributed over every continent and almost every terrestrial habitat. There are many more species in the ], especially in ], than in temperate zones.{{sfn|Gullan|Cranston|2014|p=8}} The world's regions have received widely differing amounts of attention from entomologists. The British Isles have been thoroughly surveyed, so that Gullan and Cranston 2014 state that the total of around 22,500 species is probably within 5% of the actual number there; they comment that Canada's list of 30,000 described species is surely over half of the actual total. They add that the 3,000 species of the American Arctic must be broadly accurate. In contrast, a large majority of the insect species of the tropics and the ] are probably undescribed.{{sfn|Gullan|Cranston|2014|p=8}} Some 30–40,000 species ]; very few insects, perhaps a hundred species, are marine.<ref name="Crook 2018">{{cite web |last1=Crook |first1=Glynis |title=Marine insects: small but significant |url=https://www.dw.com/en/why-are-there-so-few-insects-at-sea/a-44388348 |publisher=Deutsche Welle |access-date=2 December 2023}}</ref> Insects such as ] flourish in cold habitats including the ] and at high altitude.<ref>{{cite journal |last=Hågvar |first=Sigmund |title=A review of Fennoscandian arthropods living on and in snow |journal=European Journal of Entomology |volume=107 |issue=3 |year=2010 |pages=281–298 |doi=10.14411/eje.2010.037 |url=http://www.eje.cz/pdfs/eje/2010/03/01.pdf |archive-url=https://web.archive.org/web/20170922003622/http://www.eje.cz/pdfs/eje/2010/03/01.pdf |archive-date=22 September 2017 |url-status=live}}</ref> Insects such as ]s, ants, beetles, and termites are adapted to some of the hottest and driest environments on earth, such as the ].<ref>{{cite web |url=http://www.desertmuseum.org/books/nhsd_inverts.php |title=Invertebrates: A Vertebrate Looks at Arthropods |publisher=Arizona-Sonora Desert Museum |access-date=2013-05-21}}</ref> | |||
== Phylogeny and evolution == | == Phylogeny and evolution == | ||
{{Main|Evolution of insects}} | |||
=== External phylogeny === | |||
{{Update|section|date=July 2017}} | |||
{| class="wikitable" style="float:right; width:20em;" | |||
Insects form a ], a natural group with a common ancestor, among the ]s.<ref name=misof>{{cite journal |last1=Misof |first1=Bernhard |display-authors=etal |title=Phylogenomics resolves the timing and pattern of insect evolution |journal=Science |date=7 November 2014 |volume=346 |issue=6210 |pages=763–767 |doi=10.1126/science.1257570 |pmid=25378627 |url=https://www.science.org/ |bibcode=2014Sci...346..763M |s2cid=36008925 |access-date=17 October 2009 |archive-url=https://web.archive.org/web/20091018132952/http://www.sciencemag.org/ |archive-date=18 October 2009 |url-status=live }}</ref> A ] analysis by Kjer et al. (2016) places the insects among the ], six-legged animals with segmented bodies; their closest relatives are the ] (bristletails).<ref name="Kjer Simon Yavorskaya 2016">{{Cite journal |last1=Kjer |first1=Karl M. |last2=Simon |first2=Chris |author2-link=Chris Simon (biologist)|last3=Yavorskaya |first3=Margarita |last4=Beutel |first4=Rolf G. |date=2016 |title=Progress, pitfalls and parallel universes: a history of insect phylogenetics |journal=Journal of the Royal Society Interface |volume=13 |issue=121 |page=121 |doi=10.1098/rsif.2016.0363 |pmid=27558853 |pmc=5014063 }}</ref> | |||
|- | |||
| | |||
{{clade| |
{{clade|style=line-height:100% | ||
|label1=] | |||
|1={{clade | |||
|1={{clade | |1={{clade | ||
|1={{clade | |||
|1=] (Insecta, ], ], ]) | |||
|1=] (springtails) ] | |||
|2=] (]s, ], ], etc.) | |||
|2=] (coneheads) ] | |||
}} | |||
|2={{clade | |||
|1=] (two-pronged bristletails) ] | |||
|2='''Insecta''' (=Ectognatha) ] | |||
}} | |||
}} | |||
}} | }} | ||
|label2=] | |||
|2={{clade | |||
|1=] | |||
|2=] (millipedes) | |||
|3=] (centipedes) | |||
|4=] | |||
}} | |||
|label3=] | |||
|3={{clade | |||
|1=]a (]s, ]s, ]s, ]s, etc.) | |||
|2=]a (sea scorpions: extinct) | |||
|3=] (horseshoe crabs) | |||
|4=] (sea spiders) | |||
}} | |||
|4=†]s (extinct) | |||
}} | |||
}} | |||
|- | |||
| | |||
A ] tree of the arthropods and related groups<ref>{{cite web |title=Arthropoda |website=Tree of Life |url=http://www.tolweb.org/Arthropoda |publisher=Tree of Life Web Project |year=1995 |accessdate=9 May 2009}}</ref> | |||
|} | |||
].]] | |||
=== Internal phylogeny === | |||
The ]ary relationship of insects to other animal groups remains unclear. | |||
The internal phylogeny is based on the works of Wipfler et al. 2019 for the ],<ref name="Wipfler Letsch Frandsen 2019">{{cite journal |last1=Wipfler |first1=Benjamin |last2=Letsch |first2=Harald |last3=Frandsen |first3=Paul B. |last4=Kapli |first4=Paschalia |last5=Mayer |first5=Christoph |last6=Bartel |first6=Daniela |last7=Buckley |first7=Thomas R. |last8=Donath |first8=Alexander |last9=Edgerly-Rooks |first9=Janice S. |last10=Fujita |first10=Mari |last11=Liu |first11=Shanlin |display-authors=5 |date=February 2019 |title=Evolutionary history of Polyneoptera and its implications for our understanding of early winged insects |journal=Proceedings of the National Academy of Sciences |volume=116 |issue=8 |pages=3024–3029 |doi=10.1073/pnas.1817794116 |pmid=30642969 |pmc=6386694 |bibcode=2019PNAS..116.3024W |doi-access=free }}</ref> Johnson et al. 2018 for the ],<ref name="Johnson 2018">{{cite journal |last1=Johnson |first1=Kevin P. |last2=Dietrich |first2=Christopher H. |last3=Friedrich |first3=Frank |last4=Beutel |first4=Rolf G. |last5=Wipfler |first5=Benjamin |last6=Peters |first6=Ralph S. |last7=Allen |first7=Julie M. |last8=Petersen |first8=Malte |last9=Donath |first9=Alexander |last10=Walden |first10=Kimberly K. O. |last11=Kozlov |first11=Alexey M. |last12=Podsiadlowski |first12=Lars |last13=Mayer |first13=Christoph |last14=Meusemann |first14=Karen |last15=Vasilikopoulos |first15=Alexandros |last16=Waterhouse |first16=Robert M. |last17=Cameron |first17=Stephen L. |last18=Weirauch |first18=Christiane |last19=Swanson |first19=Daniel R. |last20=Percy |first20=Diana M. |last21=Hardy |first21=Nate B. |last22=Terry |first22=Irene |last23=Liu |first23=Shanlin |last24=Zhou |first24=Xin |last25=Misof |first25=Bernhard |last26=Robertson |first26=Hugh M. |last27=Yoshizawa |first27=Kazunori |display-authors=5 |title=Phylogenomics and the evolution of hemipteroid insects |journal=Proceedings of the National Academy of Sciences |volume=115 |issue=50 |date=26 November 2018 |issn=0027-8424 |doi=10.1073/pnas.1815820115 |pages=12775–12780 |pmid=30478043 |pmc=6294958 |bibcode=2018PNAS..11512775J |doi-access=free }}</ref> and Kjer et al. 2016 for the ].<ref name=Kjer>{{Cite journal |last1=Kjer |first1=Karl M. |last2=Simon |first2=Chris |author2-link=Chris Simon (biologist) |last3=Yavorskaya |first3=Margarita |last4=Beutel |first4=Rolf G. |date=2016 |title=Progress, pitfalls and parallel universes: a history of insect phylogenetics |journal=Journal of the Royal Society Interface |volume=13 |issue=121 |page=121 |doi=10.1098/rsif.2016.0363 |pmid=27558853 |pmc=5014063 }}</ref> The numbers of described ] species (boldface for groups with over 100,000 species) are from Stork 2018.<ref name="Stork2018"/> | |||
Although traditionally grouped with ]s and ]s—possibly on the basis of convergent adaptations to terrestrialisation<ref name="Garwood">{{cite journal |author1=Russell Garwood |author2=Gregory Edgecombe |year=2011 |title=''Early terrestrial animals, evolution and uncertainty'' |journal=] |volume=4 |issue=3 |pages=489–501 |doi=10.1007/s12052-011-0357-y |url=https://www.academia.edu/891357}}</ref>—evidence has emerged favoring closer ] with ]s. In the ] theory, insects, together with ], ], and ], make up a natural ] labeled ].<ref>{{cite web | title=Palaeos invertebrates:Arthropoda | url=http://www.palaeos.com/Invertebrates/Arthropods/Pancrustacea.html | publisher=Palaeos Invertebrates | date=3 May 2002 | accessdate=6 May 2009 | archiveurl=https://web.archive.org/web/20090215010139/http://palaeos.com/Invertebrates/Arthropods/Pancrustacea.html | archivedate=15 February 2009}}</ref> | |||
{{clade|style=font-size:85%;line-height:85% | |||
Insects form a single clade, closely related to crustaceans<!--not a clade--> and ]s.<ref name=misof>{{cite journal |last1=Misof, et.al. |first1=Bernhard |title=Phylogenomics resolves the timing and pattern of insect evolution |journal=Science |date=7 November 2014 |volume=346 |issue=6210 |pages=763–767 |doi=10.1126/science.1257570 |pmid=25378627 |url=http://www.sciencemag.org|bibcode = 2014Sci...346..763M}}</ref> | |||
|label1='''Insecta''' | |||
|1={{clade | |||
|label1=] | |||
|1=] (hump-backed/jumping bristletails, 513 spp) ] | |||
|label2=] | |||
|2={{clade | |||
|1=] (silverfish, firebrats, fishmoths, 560 spp) ] | |||
|label2=] | |||
|sublabel2='']'' | |||
|2={{clade | |||
|label1=] | |||
|1={{clade | |||
|1=] (dragonflies and damselflies, 5,899 spp) ] | |||
|2=] (mayflies, 3,240 spp) ] | |||
}} | |||
|label2=] | |||
|sublabel2=''wings flex over abdomen'' | |||
|2={{clade | |||
|label1=] | |||
|1={{clade | |||
|1={{clade | |||
|1=] (angel insects, 37 spp) ] | |||
|2=] (earwigs, 1,978 spp) ] | |||
}} | |||
|2={{clade | |||
|1=] (stoneflies, 3,743 spp) ] | |||
|2={{clade | |||
|1=] (grasshoppers, crickets, katydids, 23,855 spp) ] | |||
|2={{clade | |||
|1={{clade | |||
|label1=] | |||
|1={{clade | |||
|1=] (ice crawlers, 34 spp) ] | |||
|2=] (gladiators, 15 spp) ] | |||
}} | |||
|2={{clade | |||
|1=] (stick insects, 3,014 spp) ] | |||
|2=] (webspinners, 463 spp) ] | |||
}} | |||
}} | |||
|label2=] | |||
|2={{clade | |||
|1=] (mantises, 2,400 spp) ] | |||
|2=] (cockroaches and termites, 7,314 spp) ] | |||
}} | |||
}} | |||
}} | |||
}} | |||
}} | |||
|label2=] | |||
|2={{clade | |||
|label1=] | |||
|1={{clade | |||
|1=] (book lice, barklice and sucking lice, 11,000 spp) ] ] | |||
|2={{clade | |||
|1=] (true bugs, '''103,590''' spp) ] | |||
|2=] (thrips, 5,864 spp) ] | |||
}} | |||
}} | |||
|label2=] | |||
|sublabel2=''larvae, pupae'' | |||
|2={{clade | |||
|label1= | |||
|1=] (sawflies, wasps, bees, ants, '''116,861''' spp) ] | |||
|label2= | |||
|2={{clade | |||
|label1=] | |||
|1={{clade | |||
|label1=] | |||
|1={{clade | |||
|1=] (twisted-wing flies, 609 spp) ] | |||
|2=] (beetles, '''386,500''' spp) ] | |||
}} | |||
|label2=] | |||
|2={{clade | |||
|1=] (snakeflies, 254 spp) ] | |||
|2={{clade | |||
|1=] (lacewings, 5,868 spp) ] | |||
|2=] (alderflies and dobsonflies, 354 spp) ] | |||
}} | |||
}} | |||
}} | |||
|label2=] | |||
|2={{clade | |||
|label1=] | |||
|1={{clade | |||
|1=] (butterflies and moths, '''157,338''' spp) ] | |||
|2=] (caddisflies, 14,391 spp) ] | |||
}} | |||
|label2=] | |||
|2={{clade | |||
|1=] (true flies, '''155,477''' spp) ] | |||
|2={{clade | |||
|1=] (scorpionflies, 757 spp) ] | |||
|2=] (fleas, 2,075 spp) ] | |||
}} | |||
}} | |||
}} | |||
}} | |||
}} | |||
}} | |||
}} | |||
}} | |||
}} | |||
}} | |||
}} | |||
=== Taxonomy === | |||
Other terrestrial arthropods, such as centipedes, millipedes, ]s, and ]s, are sometimes confused with insects since their body plans can appear similar, sharing (as do all arthropods) a jointed exoskeleton. However, upon closer examination, their features differ significantly; most noticeably, they do not have the six-legged characteristic of adult insects.<ref>{{cite web | title=Evolution of insect flight | url=http://dml.cmnh.org/1994Oct/msg00116.html | publisher=Malcolm W. Browne | date=25 October 1994 | accessdate=6 May 2009}}</ref> | |||
==== Early ==== | |||
The higher-level ] of the arthropods continues to be a matter of debate and research. In 2008, researchers at ] uncovered what they believe is the world's oldest known full-body impression of a primitive flying insect, a 300-million-year-old specimen from the ].<ref>{{cite web |title=Researchers Discover Oldest Fossil Impression of a Flying Insect |date=14 October 2008 |publisher=Newswise |url=http://newswise.com/articles/view/545296/ |accessdate=21 September 2014}}</ref> The oldest definitive insect fossil is the ] '']'', from the 396-million-year-old ]. It may have superficially resembled a modern-day ] insect. This species already possessed dicondylic mandibles (two articulations in the mandible), a feature associated with winged insects, suggesting that wings may already have evolved at this time. Thus, the first insects probably appeared earlier, in the ] period.<ref name="EngelGrim">{{cite journal |last=Engel | first=Michael S. |author2=David A. Grimaldi | year=2004 | title=New light shed on the oldest insect | journal=Nature |volume=427 | pages=627–630 | doi=10.1038/nature02291 | pmid=14961119 | issue=6975|bibcode = 2004Natur.427..627E}}</ref><ref>{{cite journal |author1=Rice, C.M. |author2=Ashcroft, W.A. |author3=Batten, D.J. |author4=Boyce, A.J. |author5=Caulfield, J.B.D. |author6=Fallick, A.E. |author7=Hole, M.J. |author8=Jones, E. |author9=Pearson, M.J. |author10=Rogers, G. |author11=Saxton, J.M. |author12=Stuart, F.M. |author13=Trewin, N.H. |author14=Turner, G. | year=1995 | title=A Devonian auriferous hot spring system, Rhynie, Scotland | journal=Journal of the Geological Society, London | volume=152 | pages=229–250 | doi=10.1144/gsjgs.152.2.0229 |issue=2|bibcode=1995JGSoc.152..229R }}</ref> | |||
{{further|Aristotle's biology#Classification|Insecta in the 10th edition of Systema Naturae}} | |||
Four super radiations of insects have occurred: ]s (evolved about 300 million years ago), ] (evolved about 250 million years ago), and ]s and ]s (evolved about 150 million years ago).<ref>{{cite journal |vauthors=Wiegmann BM, Trautwein MD, Winkler IS, Barr NB, Kim JW, Lambkin C, Bertone MA, Cassel BK, Bayless KM, Heimberg AM, Wheeler BM, Peterson KJ, Pape T, Sinclair BJ, Skevington JH, Blagoderov V, Caravas J, Kutty SN, Schmidt-Ott U, Kampmeier GE, Thompson FC, Grimaldi DA, Beckenbach AT, Courtney GW, Friedrich M, Meier R, Yeates DK |year=2011 |title=Episodic radiations in the fly tree of life |journal=] |volume=108 |issue=14 |pages=5690–5695 |doi=10.1073/pnas.1012675108 |pmid=21402926 |pmc=3078341|bibcode = 2011PNAS..108.5690W}}</ref> These four groups account for the majority of described species. The flies and moths along with the ]s evolved from the ]. | |||
{{cladogram|title=Diagram of Linnaeus's key to his seven orders of insect, 1758<ref name="Winsor 1976"/> | |||
The origins of ] remain obscure, since the earliest winged insects currently known appear to have been capable fliers. Some extinct insects had an additional pair of winglets attaching to the first segment of the thorax, for a total of three pairs. As of 2009, no evidence suggests the insects were a particularly successful group of animals before they evolved to have wings.<ref>{{cite book |author1 =] |author2 =] | title=Evolution of the Insects | year=2005 | publisher=] | isbn=978-0-521-82149-0}}</ref> | |||
{{clade|style=font-size:85%;line-height:95% | |||
|sublabel1=''']''' | |||
|1={{clade | |||
|sublabel1=wingless | |||
|label1=] | |||
|1=] | |||
|sublabel2=winged | |||
|2={{clade | |||
|sublabel1=2-winged | |||
|label1=] | |||
|1=] | |||
|sublabel2=4-winged | |||
|2={{clade | |||
|sublabel1=dissimilar pairs | |||
|1={{clade | |||
|sublabel1=forewings fully hardened | |||
|label1=] | |||
|1=] | |||
|sublabel2=forewings partly hardened | |||
|label2=] | |||
|2=] | |||
}} | |||
|sublabel2=similar pairs | |||
|2={{clade | |||
|sublabel1=wings scaly | |||
|label1=] | |||
|1=] | |||
|sublabel2=wings membranous | |||
|2={{clade | |||
|sublabel1=no sting | |||
|label1=] | |||
|1=] | |||
|sublabel2=sting | |||
|label2=] | |||
|2=] | |||
}} | |||
}} | |||
}} | |||
}} | |||
}} | |||
}} | |||
}} | |||
] was the first to describe the insects as a distinct group. He placed them as the second-lowest level of animals on his '']'', above the ] sponges and worms, but below the hard-shelled marine snails. His classification remained in use for many centuries.<ref>{{cite book |last=Leroi |first=Armand Marie |author-link=Armand Marie Leroi |title=The Lagoon: How Aristotle Invented Science |title-link=Aristotle's Lagoon |publisher=Bloomsbury |date=2014 |isbn=978-1-4088-3622-4 |pages=111–119}}</ref> | |||
] and Early ] insect orders include both ] groups, their stem groups,<ref name="Archi">{{cite journal|title=X-ray micro-tomography of Carboniferous stem-Dictyoptera: New insights into early insects|first=Russell J.|last=Garwood|first2=Mark D.|last2=Sutton|year=2010|journal=Biology Letters|volume=6|issue=5|pages=699–702|url=http://rsbl.royalsocietypublishing.org/content/6/5/699.abstract|accessdate=9 June 2015 |doi=10.1098/rsbl.2010.0199|pmid=20392720|pmc=2936155}}</ref> and a number of ] groups, now extinct. During this era, some giant dragonfly-like forms reached wingspans of {{convert|55|to|70|cm|in|abbr=on}}, making them far larger than any living insect. This gigantism may have been due to higher ] levels that allowed increased respiratory efficiency relative to today. The lack of flying vertebrates could have been another factor. Most extinct orders of insects developed during the Permian period that began around 270 million years ago. Many of the early groups became extinct during the ], the largest mass extinction in the history of the Earth, around 252 million years ago.<ref name="History of Insects">{{cite book|author1 =] |author2 =Quicke, D.L.J.|title=History of Insects|year=2002|publisher=]|isbn=978-1-4020-0026-3}}</ref> | |||
In 1758, in his '']'',<ref name=Linn1758>{{cite book |last=Linnaeus |first=Carl |author-link=Carl Linnaeus |title=Systema naturae per regna tria naturae :secundum classes, ordines, genera, species, cum characteribus, differentiis, synonymis, locis. |edition=] |publisher=Holmiae (Laurentii Salvii) |year=1758 |url=https://www.biodiversitylibrary.org/bibliography/542 |access-date=22 September 2008 |language=la |archive-url=https://web.archive.org/web/20081010032456/https://www.biodiversitylibrary.org/bibliography/542 |archive-date=10 October 2008 |url-status=live}}</ref> ] divided the animal kingdom into six classes including ]. He created seven orders of insect according to the structure of their wings. These were the wingless Aptera, the two-winged Diptera, and five four-winged orders: the Coleoptera with fully-hardened forewings; the Hemiptera with partly-hardened forewings; the Lepidoptera with scaly wings; the Neuroptera with membranous wings but no ]; and the Hymenoptera, with membranous wings and a sting.<ref name="Winsor 1976">{{cite journal |last=Winsor |first=Mary P. |year=1976 |title=The development of Linnaean insect classification |journal=] |volume=25 |issue=1 |pages=57–67 |jstor=1220406 |doi=10.2307/1220406 }}</ref> | |||
The remarkably successful ] appeared as long as 146 million years ago in the ] period, but achieved their wide diversity more recently in the ] era, which began 66 million years ago. A number of highly successful insect groups evolved in conjunction with ], a powerful illustration of coevolution.<ref name="Biology-coevolution">{{cite web|author=J. Stein Carter |title=Coevolution and Pollination |url=http://biology.clc.uc.edu/courses/bio303/coevolution.htm |publisher=University of Cincinnati |date=29 March 2005 |accessdate=9 May 2009 |deadurl=yes |archiveurl=https://web.archive.org/web/20090430183230/http://biology.clc.uc.edu/Courses/bio303/coevolution.htm |archivedate=30 April 2009}}</ref> | |||
], in his 1809 '']'', treated the insects as one of nine invertebrate ].<ref name=Gould2011>{{cite book |last=Gould |first=Stephen Jay |author-link=Stephen Jay Gould |title=The Lying Stones of Marrakech |url={{GBurl|id=wApMpVmi-5gC|p=130}} |year=2011 |publisher=Harvard University Press |isbn=978-0-674-06167-5 |pages=130–134}}</ref> In his 1817 '']'', ] grouped all animals into four ''embranchements'' ("branches" with different body plans), one of which was the articulated animals, containing arthropods and annelids.<ref>{{cite book |last=De Wit |first=Hendrik C. D. |title=Histoire du Développement de la Biologie, Volume III |publisher=Presses Polytechniques et Universitaires Romandes |date=1994 |pages=94–96 |isbn=978-2-88074-264-5}}</ref> This arrangement was followed by the embryologist ] in 1828, the zoologist ] in 1857, and the comparative anatomist ] in 1860.<ref name=Valentine2004/> In 1874, ] divided the animal kingdom into two subkingdoms, one of which was Metazoa for the multicellular animals. It had five phyla, including the articulates.<ref>{{cite book |last1=Haeckel |first1=Ernst |author-link=Ernst Haeckel |title=Anthropogenie oder Entwickelungsgeschichte des menschen |url=https://archive.org/details/anthropogenieod05haecgoog |year=1874 |page=202 |language=de |publisher=W. Engelmann }}</ref><ref name=Valentine2004>{{cite book |last=Valentine |first=James W. |title=On the Origin of Phyla |url={{GBurl|id=DMBkmHm5fe4C|p=8}} |year=2004 |publisher=University of Chicago Press |isbn=978-0-226-84548-7 |pages=7–8}}</ref> | |||
Many modern insect ] developed during the Cenozoic. Insects from this period on are often found preserved in ], often in perfect condition. The body plan, or ], of such specimens is thus easily compared with modern species. The study of fossilized insects is called ]. | |||
=== |
==== Modern ==== | ||
Insects are prey for a variety of organisms, including terrestrial vertebrates. The earliest vertebrates on land existed 400 million years ago and were large amphibious ]s. Through gradual evolutionary change, ] was the next diet type to evolve.<ref name="SahneyBentonFerry2010RainforestCollapse">{{cite journal | doi=10.1130/G31182.1 |last1=Sahney |first1=S. |last2=Benton |first2=M.J. |last3=Falcon-Lang |first3=H.J. |date=2010 |title=Rainforest collapse triggered Pennsylvanian tetrapod diversification in Euramerica |journal=Geology |volume=38 |issue=12 |pages=1079–1082 |bibcode=2010Geo....38.1079S}}</ref> | |||
Insects were among the earliest terrestrial ]s and acted as major selection agents on plants.<ref name="Biology-coevolution" /> Plants evolved chemical ] and the insects, in turn, evolved mechanisms to deal with plant toxins. Many insects make use of these toxins to protect themselves from their predators. Such insects often advertise their toxicity using warning colors.<ref name="autogenerated2">{{cite web|title=Coevolution and Pollination |url=http://biology.clc.uc.edu/courses/bio303/coevolution.htm |publisher=University of Cincinnati |accessdate=9 May 2009 |deadurl=yes |archiveurl=https://web.archive.org/web/20090430183230/http://biology.clc.uc.edu/Courses/bio303/coevolution.htm |archivedate=30 April 2009}}</ref> This successful evolutionary pattern has also been used by ]s. Over time, this has led to complex groups of coevolved species. Conversely, some interactions between plants and insects, like ], are beneficial to both organisms. Coevolution has led to the development of very specific ] in such systems. | |||
===Taxonomy=== | |||
{{See also|Category:Insect orders|Category:Insect families}} | {{See also|Category:Insect orders|Category:Insect families}} | ||
{| class="wikitable" style="float:right; width:20em;" | |||
|- | |||
| | |||
{| style="background:Transparent; border:solid 0 #503df9;" | |||
|- | |||
! colspan="4" style="background:#E6D09D"| Classification | |||
|- | |||
| <div style="width:105%; max-height:600px; overflow:auto;"> | |||
|- | |||
| rowspan="4" style="background:#ECF4ED"| '''Insecta''' | |||
| colspan="3" style="background:#ECF4ED"| | |||
{| class="collapsible collapsed" style="float:right; background:Transparent;" | |||
|- | |||
! ] | |||
|- | |||
| style="border-top: 1px solid black;"| -] <small>- 470</small> | |||
|} | |||
|- | |||
| rowspan="3" style="background:#ECF4ED"| ''']''' | |||
| colspan="2" style="background:#ECF4ED"| | |||
{| class="collapsible collapsed" style="float:right; background:Transparent;" | |||
|- | |||
! ] | |||
|- | |||
| style="border-top: 1px solid black;"| -]<small><200 </small> | |||
|- | |||
| -] | |||
|} | |||
|- | |||
| rowspan="2" style="background:#ECF4ED"| ''']''' | |||
| style="background:#ECF4ED"| | |||
{| class="collapsible collapsed" style="float:right; background:Transparent;" | |||
|- | |||
! ] | |||
|- | |||
| style="border-top: 1px solid black;"| -]<small>- 2,500–<3,000</small> | |||
|- | |||
| -]<small>- 6,500 </small> | |||
|} | |||
|- | |||
| style="background:#ECF4ED"| | |||
{| class="collapsible collapsed" style="float:right; background:Transparent;" | |||
|- | |||
! ] | |||
|- | |||
| style="border-top: 1px solid black;"| -]<small> – 3,684–4,000</small> | |||
|- | |||
| -]<small> – 360,000–400,000</small> | |||
|- | |||
| -]<small> – 1,816</small> | |||
|- | |||
| -]<small> – 152,956</small> | |||
|- | |||
| -]<small> – 200–300</small> | |||
|- | |||
| -]<small> – 50,000–80,000</small> | |||
|- | |||
| -]<small> – 115,000</small> | |||
|- | |||
| -]<small> – 174,250</small> | |||
|- | |||
| -]<small> – 2,200</small> | |||
|- | |||
| -]<small> – 481</small> | |||
|- | |||
| -]<small> – 250–300</small> | |||
|- | |||
| -]<small> – 5,000</small> | |||
|- | |||
| -]<small> – 30</small> | |||
|- | |||
| -]<small> – 24,380</small> | |||
|- | |||
| -]<small> – 2,500–3,300</small> | |||
|- | |||
| -]<small> – 3,000–3,200</small> | |||
|- | |||
| -]<small> – 2,274</small> | |||
|- | |||
| -]<small> – 5,500</small> | |||
|- | |||
| -]<small> – 210</small> | |||
|- | |||
| -]<small> – 2,525</small> | |||
|- | |||
| -]<small> – 596</small> | |||
|- | |||
| -]<small> – 5,000</small> | |||
|- | |||
| -]<small> – 12,627</small> | |||
|- | |||
| -]<small> – 28</small> | |||
|} | |||
|} | |||
|- | |||
| | |||
] of living insect groups,<ref>{{cite web | title=Insecta | url=http://www.tolweb.org/Insecta/8205| publisher=Tree of Life Web Project | year=2002 | accessdate=12 May 2009}}</ref> with numbers of species in each group.<ref name="number" /> The ], ], and ] are possibly ] groups. | |||
|} | |||
Traditional morphology |
Traditional morphology-based ] have usually given the ] the rank of ],{{sfn|Gullan|Cranston|2005|p=180}} and identified four groups within it: insects (Ectognatha), ], ], and ], the latter three being grouped together as the ] on the basis of internalized mouth parts.<ref name="Kendall 2009"/> | ||
Insects can be divided into two groups historically treated as subclasses: wingless insects |
The use of phylogenetic data has brought about numerous changes in relationships above the level of ].<ref name="Kendall 2009">{{cite web |title=Classification of Bugs |last=Kendall |first=David A. |url=http://www.kendall-bioresearch.co.uk/class.htm |year=2009 |access-date=9 May 2009 |url-status=dead |archive-url=https://web.archive.org/web/20090520201746/http://www.kendall-bioresearch.co.uk/class.htm |archive-date=20 May 2009 |df=dmy-all }}</ref> Insects can be divided into two groups historically treated as subclasses: wingless insects or ], and winged insects or ]. The Apterygota traditionally consisted of the primitively wingless orders ] (jumping bristletails) and ] (silverfish). However, Apterygota is not ], as Archaeognatha are sister to all other insects, based on the arrangement of their ], while the Pterygota, the winged insects, emerged from within the ], alongside the Zygentoma.<ref name="BlankeEtal">{{cite journal |last1=Blanke |first1=Alexander |last2=Machida |first2=Ryuichiro |last3=Szucsich |first3=Nikolaus Urban |last4=Wilde |first4=Fabian |last5=Misoe |first5=Bernhard |title=Mandibles with two joints evolved much earlier in the history of insects: dicondyly is a synapomorphy of bristletails, silverfish and winged insects |journal=Systematic Entomology |publisher=Wiley |volume=40 |issue=2 |date=15 October 2014 |doi=10.1111/syen.12107 |pages=357–364 |s2cid=85309726 }}</ref> | ||
The Pterygota (] and ]) are winged and have ] on the outside of their body segments; the Neoptera have muscles that allow their wings to fold flat over the abdomen. Neoptera can be divided into groups with incomplete metamorphosis (] and ]) and those with complete metamorphosis (]). The molecular finding that the traditional ] orders ] and ] are within ] has led to the new taxon ].<ref>{{cite journal |last1=Johnson |first1=K. P. |last2=Yoshizawa |first2=K. |last3=Smith |first3=V. S. |year=2004 |title=Multiple origins of parasitism in lice |journal=Proceedings of the Royal Society of London |volume=271 |issue=1550 |pages=1771–1776 |doi=10.1098/rspb.2004.2798 |pmid=15315891 |pmc=1691793}}</ref> ] and ] have been suggested to form the Eukinolabia.<ref>{{cite journal |author1=Terry, M. D. |author2=Whiting, M. F. |year=2005 |title=Mantophasmatodea and phylogeny of the lower neopterous insects |doi=10.1111/j.1096-0031.2005.00062.x |url=https://www.researchgate.net/publication/227604832 |journal=Cladistics |volume=21 |issue=3 |pages=240–257 |s2cid=86259809 |doi-access=free }}</ref> Mantodea, Blattodea, and Isoptera form a monophyletic group, ].<ref>{{cite journal |doi=10.1016/S0960-9822(00)00561-3 |year=2000 |first1=Nathan |last1=Lo |first2=Gaku |last2=Tokuda |first3=Hirofumi |last3=Watanabe |first4=Harley |last4=Rose |first5=Michael |last5=Slaytor |first6=Kiyoto |last6=Maekawa |first7=Claudio |last7=Bandi |first8=Hiroaki |last8=Noda |display-authors=5 |title=Evidence from multiple gene sequences indicates that termites evolved from wood-feeding cockroaches |journal=Current Biology |volume=10 |issue= 13|pages=801–804 |pmid=10898984|s2cid=14059547 |doi-access=free |bibcode=2000CBio...10..801L }}</ref> Fleas are now thought to be closely related to boreid mecopterans.<ref>{{cite journal |last=Whiting |first=M. F. |title=Mecoptera is paraphyletic: multiple genes and phylogeny of Mecoptera and Siphonaptera |year=2002 |journal=Zoologica Scripta |volume=31 |issue=1 |pages=93–104 |doi=10.1046/j.0300-3256.2001.00095.x |s2cid=56100681 }}</ref> | |||
=== Evolutionary history === | |||
The Exopterygota likely are paraphyletic in regard to the Endopterygota. Matters that have incurred controversy include Strepsiptera and Diptera grouped together as Halteria based on a reduction of one of the wing pairs—a position not well-supported in the entomological community.<ref>{{cite journal|author1=Bonneton, F. |author2=Brunet, F.G. |author3=Kathirithamby J. |author4=Laudet, V. |lastauthoramp=yes |year=2006|title= The rapid divergence of the ecdysone receptor is a synapomorphy for Mecopterida that clarifies the Strepsiptera problem|pmid=16756554|journal= Insect Molecular Biology |volume=15|issue=3|pages=351–362|doi=10.1111/j.1365-2583.2006.00654.x}}</ref> The Neuropterida are often lumped or split on the whims of the taxonomist. Fleas are now thought to be closely related to boreid mecopterans.<ref>{{cite journal |author=Whiting, M.F.|year= 2002|title= Mecoptera is paraphyletic: multiple genes and phylogeny of Mecoptera and Siphonaptera|journal= Zoologica Scripta |volume=31|issue=1|pages= 93–104|doi=10.1046/j.0300-3256.2001.00095.x}}</ref> Many questions remain in the basal relationships among endopterygote orders, particularly the Hymenoptera. | |||
{{main|Evolution of insects}} | |||
The study of the classification or taxonomy of any insect is called ]. If one works with a more specific order or even a family, the term may also be made specific to that order or family, for example ]. | |||
The oldest fossil that may be a primitive wingless insect is '']'' from the Early ] ].<ref>{{Cite journal |last=Ross |first=Andrew |date=August 2022 |title=Evolution: The origin of insect wings revisited |journal=Current Biology |volume=32 |issue=15 |pages=R851–R853 |doi=10.1016/j.cub.2022.06.087|pmid=35944489 |s2cid=251464185 |doi-access=free |bibcode=2022CBio...32.R851R }}</ref> The oldest known flying insects are from the mid-], around 328–324 million years ago. The group subsequently underwent a rapid ]. Claims that they originated substantially earlier, during the ] or ] (some 400 million years ago) based on ] estimates, are unlikely to be correct, given the fossil record.<ref>{{cite journal |last1=Schachat |first1=Sandra R. |last2=Goldstein |first2=Paul Z. |last3=Desalle |first3=Rob |last4=Bobo |first4=Dean M. |last5=Boyce |first5=C. Kevin |last6=Payne |first6=Jonathan L. |last7=Labandeira |first7=Conrad C. |date=2023-02-02 |title=Illusion of flight? Absence, evidence and the age of winged insects |url=https://academic.oup.com/biolinnean/article/138/2/143/6936511 |journal=Biological Journal of the Linnean Society |volume=138 |issue=2 |pages=143–168 |doi=10.1093/biolinnean/blac137 |doi-access=free }}</ref> | |||
== Diversity == | |||
{{Main|Insect biodiversity}} | |||
Four ] of insects have occurred: ]s (from about 300 million years ago), ] (from about 250 million years ago), ]s and ]s (both from about 150 million years ago).<ref name="Wiegmann Trautwein Winkler Barr 2011">{{cite journal |last1=Wiegmann |first1=Brian M. |last2=Trautwein |first2=Michelle D. |last3=Winkler |first3=Isaac S. |last4=Barr |first4=Norman B. |last5=Kim |first5=Jung-Wook |last6=Lambkin |first6=Christine |last7=Bertone |first7=Matthew A. |last8=Cassel |first8=Brian K. |last9=Bayless |first9=Keith M. |last10=Heimberg |first10=Alysha M. |last11=Wheeler |first11=Benjamin M. |last12=Peterson |first12=Kevin J. |last13=Pape |first13=Thomas |last14=Sinclair |first14=Bradley J. |last15=Skevington |first15=Jeffrey H. |last16=Blagoderov |first16=Vladimir |last17=Caravas |first17=Jason |last18=Kutty |first18=Sujatha Narayanan |last19=Schmidt-Ott |first19=Urs |last20=Kampmeier |first20=Gail E. |last21=Thompson |first21=F. Christian |last22=Grimaldi |first22=David A. |last23=Beckenbach |first23=Andrew T. |last24=Courtney |first24=Gregory W. |last25=Friedrich |first25=Markus |last26=Meier |first26=Rudolf |last27=Yeates |first27=David K. |display-authors=5 |date=14 March 2011 |title=Episodic radiations in the fly tree of life |journal=Proceedings of the National Academy of Sciences |volume=108 |issue=14 |pages=5690–5695 |bibcode=2011PNAS..108.5690W |doi=10.1073/pnas.1012675108 |pmc=3078341 |pmid=21402926 |doi-access=free }}</ref><!-- These four groups account for the majority of described species.--> | |||
Though the true dimensions of species diversity remain uncertain, estimates range from 2.6–7.8 million species with a mean of 5.5 million.<ref name="Stork2015">{{Cite journal | |||
| pmid = 26034274 | |||
| pmc = 4475949 | |||
| year = 2015 | |||
| author1 = Stork | |||
| first1 = N.E. | |||
| title = New approaches narrow global species estimates for beetles, insects, and terrestrial arthropods | |||
| journal = Proceedings of the National Academy of Sciences | |||
| last2 = McBroom | |||
| first2 = J | |||
| last3 = Gely | |||
| first3 = C | |||
| last4 = Hamilton | |||
| first4 = A.J. | |||
| doi = 10.1073/pnas.1502408112 | |||
| volume=112 | |||
| issue = 24 | |||
| pages = 7519–7523 | |||
| bibcode = 2015PNAS..112.7519S | |||
}}</ref> | |||
The remarkably successful ] (wasps, bees, and ants) appeared some 200 million years ago in the ] period, but achieved their wide diversity more recently in the ] era, which began 66 million years ago. Some highly successful insect groups evolved in conjunction with ]s, a powerful illustration of ]. Insects were among the earliest terrestrial ]s and acted as major selection agents on plants.<ref name="Biology-coevolution">{{cite web |last=Carter |first=J. Stein |date=29 March 2005 |title=Coevolution and Pollination |url=http://biology.clc.uc.edu/courses/bio303/coevolution.htm |url-status=dead |archive-url=https://web.archive.org/web/20090430183230/http://biology.clc.uc.edu/Courses/bio303/coevolution.htm |archive-date=30 April 2009 |access-date=9 May 2009 |publisher=University of Cincinnati}}</ref> Plants evolved chemical ] and the insects, in turn, evolved mechanisms to deal with plant toxins. Many insects make use of these toxins to protect themselves from their predators. Such insects often advertise their toxicity using ].<ref name="autogenerated2">{{cite web|title=Coevolution and Pollination |url=http://biology.clc.uc.edu/courses/bio303/coevolution.htm |publisher=] |access-date=9 May 2009 |url-status=dead |archive-url=https://web.archive.org/web/20090430183230/http://biology.clc.uc.edu/Courses/bio303/coevolution.htm |archive-date=30 April 2009}}</ref> | |||
] species, showing just over half of these to be insects]] | |||
Between 950,000–1,000,000 of all described species are insects, so over 50% of all described eukaryotes (1.8 million) are insects (see illustration). With only 950,000 known non-insects, if the actual number of insects is 5.5 million, they may represent over 80% of the total, and with only about 20,000 new species of all organisms being described each year, most insect species likely will remain undescribed, unless species descriptions greatly increase in rate. Of the 24 orders of insects, four dominate in terms of numbers of described species, with at least 670,000 species included in ], ], ] and ]. | |||
<gallery mode=packed heights=180px> | |||
<center> | |||
File:Meganeura monyi au Museum de Toulouse.jpg|The giant dragonfly-like insect '']'' grew to wingspans of {{cvt|75|cm|ftin|0}} in the late ], around 300 million years ago.<ref>{{cite book |last1=Taylor |last2=Lewis |year=2007 |title=Fossil Invertebrates |first1=Paul D. |first2=David N. |edition=repeated |publisher=] |isbn=978-0674025745 |page=160 |url=https://books.google.com/books?id=7kPwZ2LeSAoC }}</ref> | |||
{| class="wikitable" style="text-align: center;" | |||
File:Moravocoleus permianus.jpg|] '']'', fossil and reconstruction, from the Early ] | |||
|+ Comparison of the estimated number of species in the four most speciose insect orders{{Citation needed|date=April 2012}} | |||
File:Fossil Wasp ( Iberomaimetsha ).jpg|] such as this '']'' from the Early ], around 100 million years ago. | |||
|- | |||
</gallery> | |||
| | |||
! scope="col" | Described species | |||
! scope="col" | Average description rate<br />(species per year) | |||
! scope="col" | Publication effort | |||
|- | |||
! scope="row" | ] | |||
| 300,000–400,000 | |||
| 2308 | |||
| 0.01 | |||
|- | |||
! scope="row" | ]<ref name="Taxome1">{{cite web |url=http://www.ucl.ac.uk/taxome/lepnos.html |title=Taxonomy of Lepidoptera: the scale of the problem |author=Mallet, Jim |date=12 June 2007 |work=The Lepidoptera Taxome Project |publisher=University College, London |accessdate=8 February 2011}}</ref> | |||
| 180,000 | |||
| 642 | |||
| 0.03 | |||
|- | |||
! scope="row" | ] | |||
| 90,000–150,000 | |||
| 1048 | |||
| 0.04 | |||
|- | |||
! scope="row" | ] | |||
| 100,000–150,000 | |||
| 1196 | |||
| 0.02 | |||
|} | |||
</center> | |||
A 2015 study estimated the number of beetle species at 0.9–2.1 million with a mean of 1.5 million.<ref name = "Stork2015"/> | |||
== Morphology and physiology == | == Morphology and physiology == | ||
{{Main|Insect morphology|Insect physiology}} | |||
{{Main|Insect morphology}} | |||
=== External === | === External === | ||
[[File:Insect anatomy diagram.svg|right|upright=1.35|thumb|Insect morphology<br /> | |||
'''A'''- Head '''B'''- Thorax '''C'''- Abdomen <br /> | |||
<div style="{{column-count|2}}"> | |||
1. ]<br /> | |||
2. ] (lower)<br /> | |||
3. ocelli (upper)<br /> | |||
4. ]<br /> | |||
5. brain (cerebral ])<br /> | |||
6. ]<br /> | |||
7. dorsal blood vessel<br /> | |||
8. ] tubes (trunk with ])<br /> | |||
9. ]<br /> | |||
10. ]<br /> | |||
11. ]<br /> | |||
12. ]<br /> | |||
13. mid-gut (stomach)<br /> | |||
14. dorsal tube (Heart)<br /> | |||
15. ovary<br /> | |||
16. ] (intestine, rectum & anus)<br /> | |||
17. anus<br /> | |||
18. oviduct<br /> | |||
19. nerve chord (abdominal ganglia)<br /> | |||
20. ]<br /> | |||
21. tarsal pads<br /> | |||
22. claws<br /> | |||
23. ]<br /> | |||
24. ]<br /> | |||
25. ]<br /> | |||
26. ]<br /> | |||
27. fore-gut (crop, gizzard)<br /> | |||
28. thoracic ganglion<br /> | |||
29. ]<br /> | |||
30. salivary gland<br /> | |||
31. ]<br /> | |||
32. ]</div>]] | |||
Insects have ] bodies supported by ]s, the hard outer covering made mostly of ]. The segments of the body are organized into three distinctive but interconnected units, or ]: a head, a ] and an ].<ref>{{cite web|title=O. Orkin Insect zoo |url=http://insectzoo.msstate.edu/Students/basic.structure.html |publisher=The University of Nebraska Department of Entomology |accessdate=3 May 2009 |deadurl=yes |archiveurl=https://web.archive.org/web/20090602045832/http://www.insectzoo.msstate.edu/Students/basic.structure.html |archivedate=2 June 2009}}</ref> The head supports a pair of sensory ], a pair of ]s, zero to three simple eyes (or ]) and three sets of variously modified appendages that form the ]. The thorax is made up of three segments: the prothorax, mesothorax and the metathorax. Each thoracic segment supports one pair of legs. The meso- and metathoracic segments may each have a pair of ], depending on the insect. The abdomen consists of eleven segments, though in a few species of insects, these segments may be fused together or reduced in size. The abdomen also contains most of the ], ], ] and reproductive internal structures.<ref name="Gullan and Cranston">{{cite book |last=Gullan |first=P.J. |author2=Cranston, P.S. |title=The Insects: An Outline of Entomology |publisher=Blackwell Publishing |location=Oxford |year=2005 |edition= 3rd |isbn=978-1-4051-1113-3}}</ref>{{Rp|22–48}} Considerable variation and many adaptations in the body parts of insects occur, especially wings, legs, antenna and mouthparts. | |||
[[File:Insect anatomy diagram.svg|right|upright=1.35|thumb|Insect morphology<br/> | |||
=== Segmentation === | |||
'''A'''- Head '''B'''- Thorax '''C'''- Abdomen | |||
The ] is enclosed in a hard, heavily sclerotized, unsegmented, exoskeletal head capsule, or ], which contains most of the sensing organs, including the antennae, ocellus or eyes, and the mouthparts. Of all the insect orders, Orthoptera displays the most features found in other insects, including the ] and ]s.<ref name="ReshCarde2009">{{cite book |last=Resh |first=Vincent H. |author2=Ring T. Carde |title=Encyclopedia of Insects |publisher=Academic Press |location=U.S |date=2009 |edition= 2 |isbn=978-0-12-374144-8}}</ref> Here, the ], or the apex (dorsal region), is situated between the compound eyes for insects with a ] and ] head. In prognathous insects, the vertex is not found between the compound eyes, but rather, where the ] are normally. This is because the primary axis of the head is rotated 90° to become parallel to the primary axis of the body. In some species, this region is modified and assumes a different name.<ref name="ReshCarde2009" />{{rp|13}} | |||
{{image key | |||
|list type=ordered | |||
|] | |||
|] (lower) | |||
|ocellus (upper) | |||
|] | |||
|brain (cerebral ]) | |||
|] | |||
|dorsal blood vessel | |||
|] tubes (trunk with ]) | |||
|] | |||
|] | |||
|] | |||
|] | |||
|midgut (stomach) | |||
|dorsal tube (heart) | |||
|ovary | |||
|] (intestine, rectum, anus) | |||
|anus | |||
|oviduct | |||
|] | |||
|] | |||
|tarsal pads | |||
|claws | |||
|] | |||
|] | |||
|] | |||
|] | |||
|foregut (crop, gizzard) | |||
|] | |||
|] | |||
|salivary gland | |||
|] | |||
|] | |||
}}]] | |||
==== Three-part body ==== | |||
The ] is a tagma composed of three sections, the ], ] and the ]. The anterior segment, closest to the head, is the prothorax, with the major features being the first pair of legs and the pronotum. The middle segment is the mesothorax, with the major features being the second pair of legs and the anterior wings. The third and most posterior segment, abutting the abdomen, is the metathorax, which features the third pair of legs and the posterior wings. Each segment is dilineated by an intersegmental suture. Each segment has four basic regions. The dorsal surface is called the tergum (or ''notum'') to distinguish it from the abdominal terga.<ref name="Gullan and Cranston" /> The two lateral regions are called the pleura (singular: pleuron) and the ventral aspect is called the sternum. In turn, the notum of the prothorax is called the pronotum, the notum for the mesothorax is called the mesonotum and the notum for the metathorax is called the metanotum. Continuing with this logic, the mesopleura and metapleura, as well as the mesosternum and metasternum, are used.<ref name="ReshCarde2009" /> | |||
Insects have a ] body supported by an ], the hard outer covering made mostly of ]. The body is organized into three ]: the ], ] and ]. The head supports a pair of sensory ], a pair of ]s, zero to three simple eyes (or ]) and three sets of variously modified appendages that form the ]. The thorax carries the three pairs of legs and up to two pairs of ]. The abdomen contains most of the digestive, respiratory, excretory and reproductive structures.{{sfn|Gullan|Cranston|2005|pp=22–48}} | |||
The ] is the largest tagma of the insect, which typically consists of 11–12 segments and is less strongly sclerotized than the head or thorax. Each segment of the abdomen is represented by a sclerotized tergum and sternum. Terga are separated from each other and from the adjacent sterna or pleura by membranes. Spiracles are located in the pleural area. Variation of this ground plan includes the fusion of terga or terga and sterna to form continuous dorsal or ventral shields or a conical tube. Some insects bear a sclerite in the pleural area called a laterotergite. Ventral sclerites are sometimes called ]s. During the embryonic stage of many insects and the postembryonic stage of primitive insects, 11 abdominal segments are present. In modern insects there is a tendency toward reduction in the number of the abdominal segments, but the primitive number of 11 is maintained during embryogenesis. Variation in abdominal segment number is considerable. If the Apterygota are considered to be indicative of the ground plan for pterygotes, confusion reigns: adult Protura have 12 segments, Collembola have 6. The orthopteran family Acrididae has 11 segments, and a fossil specimen of Zoraptera has a 10-segmented abdomen.<ref name="ReshCarde2009" /> | |||
==== Segmentation ==== | |||
{{further|Insect morphology}} | |||
The head is enclosed in a hard, heavily ], unsegmented ], which contains most of the sensing organs, including the antennae, compound eyes, ocelli, and mouthparts.{{sfn|Resh|Carde|2009|p=13}} The thorax is composed of three sections named (from front to back) the ], ] and ]. The prothorax carries the first pair of legs. The mesothorax carries the second pair of legs and the front wings. The metathorax carries the third pair of legs and the hind wings.{{sfn|Gullan|Cranston|2005|pp=22–48}}{{sfn|Resh|Carde|2009|p=13}} The abdomen is the largest part of the insect, typically with 11–12 segments, and is less strongly sclerotized than the head or thorax. Each segment of the abdomen has sclerotized upper and lower plates (the tergum and sternum), connected to adjacent sclerotized parts by membranes. Each segment carries a pair of ]s.{{sfn|Resh|Carde|2009|p=13}} | |||
==== Exoskeleton ==== | ==== Exoskeleton ==== | ||
The insect outer skeleton, the cuticle, is made up of two layers: the ], which is a thin and waxy water resistant outer layer and contains no ], and a lower layer called the ]. The procuticle is chitinous and much thicker than the epicuticle and has two layers: an outer layer known as the exocuticle and an inner layer known as the endocuticle. The tough and flexible endocuticle is built from numerous layers of fibrous chitin and proteins, criss-crossing each other in a sandwich pattern, while the exocuticle is rigid and ].<ref name="Gullan and Cranston" />{{Rp|22–24}} The exocuticle is greatly reduced in many soft-bodied insects (e.g., ]s), especially during their ]l stages. | |||
{{main|Arthropod cuticle}} | |||
Insects are the only ]s to have developed active flight capability, and this has played an important role in their success.<ref name="Gullan and Cranston" />{{Rp|186}} Their muscles are able to contract multiple times for each single nerve impulse, allowing the wings to beat faster than would ordinarily be possible. Having their muscles attached to their exoskeletons is more efficient and allows more muscle connections; ]s also use the same method, though all ]s use ] pressure to extend their legs, a system inherited from their pre-arthropod ancestors. Unlike insects, though, most aquatic crustaceans are ] with ] extracted from the water.<ref>{{cite book |author1=Barnes, R.S.K. |author2=Calow, P. |author3=Olive, P. |author4=Golding, D. |author5=and Spicer, J. | title=The Invertebrates: A Synthesis | publisher=Blackwell Publishing | year=2001 | isbn=978-0-632-04761-1 | chapter=Invertebrates with Legs: the Arthropods and Similar Groups | page=168| chapter-url=https://books.google.com/?id=TBMsbe9efPgC&pg=PA168}}</ref><ref>{{cite book |author1=Lowenstam, H.A. |author2=Weiner, S. | title=On biomineralization| publisher=Oxford University Press US | year=1989 | isbn=978-0-19-504977-0| page=111 | url=https://books.google.com/?id=JbAgy0AAopsC}}</ref> | |||
The outer skeleton, the ], is made up of two layers: the epicuticle, a thin and waxy water-resistant outer layer without ], and a lower layer, the thick chitinous procuticle. The procuticle has two layers: an outer exocuticle and an inner endocuticle. The tough and flexible endocuticle is built from numerous layers of fibrous chitin and proteins, criss-crossing each other in a sandwich pattern, while the exocuticle is rigid and sclerotized.{{sfn|Gullan|Cranston|2005|p=22–24}}<ref>{{Cite journal |last=Belles |first=Xavier |title=The innovation of the final moult and the origin of insect metamorphosis |date=14 October 2019 |journal=Philosophical Transactions of the Royal Society B: Biological Sciences |volume=374 |issue=1783 |pages=20180415 |doi=10.1098/rstb.2018.0415 |pmid=31438822 |pmc=6711288}}</ref> As an adaptation to life on land, insects have an ] <!--multicopper oxidase-2--> that uses atmospheric oxygen to harden their cuticle, unlike crustaceans which use heavy calcium compounds for the same purpose. This makes the insect exoskeleton a lightweight material.<ref name=AsanHashEver23>{{Cite journal |last1=Asano |first1=Tsunaki |last2=Hashimoto |first2=Kosei |last3=Everroad |first3=R. Craig |date=2023 |title=Eco-evolutionary implications for a possible contribution of cuticle hardening system in insect evolution and terrestrialisation |journal=Physiological Entomology |volume=48 |issue=2–3 |pages=55–60 |doi=10.1111/phen.12406 |s2cid=258209514 |doi-access=free }}</ref> | |||
=== Internal === | |||
=== Internal systems === | |||
The ] of an insect can be divided into a ] and a ]. The head capsule is made up of six fused segments, each with either a pair of ], or a cluster of nerve cells outside of the brain. The first three pairs of ganglia are fused into the brain, while the three following pairs are fused into a structure of three pairs of ganglia under the insect's ], called the ].<ref name="Gullan and Cranston" />{{Rp|57}} | |||
{{main|Insect physiology}} | |||
The ] segments have one ganglion on each side, which are connected into a pair, one pair per segment. This arrangement is also seen in the abdomen but only in the first eight segments. Many species of insects have reduced numbers of ganglia due to fusion or reduction.<ref name="INSECTS: ROLE OF THE SPIRACLES">{{cite journal|doi=10.2307/1539265|last=Schneiderman|first=Howard A.|year=1960|title=Discontinuous respiration in insects: role of the spiracles|journal=] |issue=3|pages=494–528|url=http://www.biolbull.org/cgi/reprint/119/3/494?maxtoshow=&HITS=10&hits=10&RESULTFORMAT=&fulltext=insect+thoracic+spiracle&andorexactfulltext=and&searchid=1&FIRSTINDEX=0&sortspec=relevance&resourcetype=HWCIT|volume=119|jstor=1539265}}</ref> Some cockroaches have just six ganglia in the abdomen, whereas the wasp '']'' has only two in the thorax and three in the abdomen. Some insects, like the house fly '']'', have all the body ganglia fused into a single large thoracic ganglion. | |||
==== Nervous ==== | |||
At least a few insects have ]s, cells that detect and transmit signals responsible for the sensation of ].<ref>{{cite journal | title=Do insects feel pain? – A biological view | journal=Cellular and Molecular Life Sciences | doi=10.1007/BF01963580 | year=1984 | volume=40 | issue=2 | pages=1420–1423| last1=Eisemann | first1=C.H. | last2=Jorgensen | first2=W.K. | last3=Merritt | first3=D.J. | last4=Rice | first4=M.J. | last5=Cribb | first5=B.W. | last6=Webb | first6=P.D. | last7=Zalucki | first7=M.P.}}</ref>{{Failed verification|date=May 2017}} This was discovered in 2003 by studying the variation in reactions of ] of the common fruitfly ] to the touch of a heated probe and an unheated one. The larvae reacted to the touch of the heated probe with a stereotypical rolling behavior that was not exhibited when the larvae were touched by the unheated probe.<ref>{{cite journal | title=painless, a Drosophila gene essential for nociception | journal=Cell | last1=Tracey | first1=J | date=2003| volume=113 | issue=2 | pages=261–273 | doi=10.1016/S0092-8674(03)00272-1 | pmid=12705873 | last2=Wilson | first2=RI | last3=Laurent | first3=G | last4=Benzer | first4=S}}</ref> Although ] has been demonstrated in insects, there is no consensus that insects feel pain consciously<ref>{{cite web | title=Sentience and pain in invertebrates | last=Sømme | first=LS | date=14 January 2005| publisher=Norwegian Scientific Committee for Food Safety | accessdate=30 September 2009 | url=<!-- http://google.com/scholar?q=cache:dbrbM20yEQ4J:scholar.google.com/&hl=en -->http://www.vkm.no/dav/413af9502e.pdf}}</ref> | |||
The ] of an insect consists of a ] and a ]. The head capsule is made up of six fused segments, each with either a pair of ], or a cluster of nerve cells outside of the brain. The first three pairs of ganglia are fused into the brain, while the three following pairs are fused into a structure of three pairs of ganglia under the insect's ], called the ].{{sfn|Gullan|Cranston|2005|p=57}} The ] segments have one ganglion on each side, connected into a pair per segment. This arrangement is also seen in the first eight segments of the abdomen. Many insects have fewer ganglia than this.<ref name="INSECTS: ROLE OF THE SPIRACLES">{{cite journal |doi=10.2307/1539265|last=Schneiderman|first=Howard A. |year=1960 |title=Discontinuous respiration in insects: role of the spiracles |journal=] |issue=3 |pages=494–528|url=http://www.biolbull.org/cgi/reprint/119/3/494?maxtoshow=&HITS=10&hits=10&RESULTFORMAT=&fulltext=insect+thoracic+spiracle&andorexactfulltext=and&searchid=1&FIRSTINDEX=0&sortspec=relevance&resourcetype=HWCIT |volume=119 |jstor=1539265 |access-date=22 May 2009 |archive-url=https://web.archive.org/web/20090625011339/http://www.biolbull.org/cgi/reprint/119/3/494?maxtoshow=&HITS=10&hits=10&RESULTFORMAT=&fulltext=insect+thoracic+spiracle&andorexactfulltext=and&searchid=1&FIRSTINDEX=0&sortspec=relevance&resourcetype=HWCIT|archive-date=25 June 2009 |url-status=live}}</ref> Insects are capable of learning.<ref>{{Cite journal |last=Dukas |first=Reuven |date=1 January 2008 |title=Evolutionary Biology of Insect Learning |url=https://www.annualreviews.org/doi/10.1146/annurev.ento.53.103106.093343|journal=Annual Review of Entomology |volume=53 |issue=1 |pages=145–160 |doi=10.1146/annurev.ento.53.103106.093343 |pmid=17803459 }}</ref> | |||
Insects are capable of learning.<ref>, ''Annual Review of Entomology'', Vol. 53: 145–160</ref> | |||
==== Digestive |
==== Digestive ==== | ||
An insect uses its digestive system to extract nutrients and other substances from the food it consumes.<ref name="genent">{{cite web | title=General Entomology – Digestive and Excritory system | url=http://www.cals.ncsu.edu/course/ent425/library/tutorials/internal_anatomy/digestive.html | publisher=NC state University | accessdate=3 May 2009}}</ref> Most of this food is ingested in the form of ]s and other complex substances like ]s, ]s, ]s and ]s. These macromolecules must be broken down by ] into smaller molecules like ]s and ]s before being used by cells of the body for energy, growth, or reproduction. This break-down process is known as ]. | |||
An insect uses its digestive system to extract nutrients and other substances from the food it consumes.<ref name="genent">{{cite web |title=General Entomology – Digestive and Excritory system |url=http://www.cals.ncsu.edu/course/ent425/library/tutorials/internal_anatomy/digestive.html |publisher=NC state University |access-date=3 May 2009 |archive-url=https://web.archive.org/web/20090523024349/http://www.cals.ncsu.edu/course/ent425/library/tutorials/internal_anatomy/digestive.html |archive-date=23 May 2009 |url-status=live }}</ref> There is extensive variation among different ], ], and even ] in the digestive system of insects.<ref>{{Cite journal |last1=Bueno |first1=Odair Correa |last2=Tanaka |first2=Francisco André Ossamu |last3=de Lima Nogueira |first3=Neusa |last4=Fox |first4=Eduardo Gonçalves Paterson |last5=Rossi |first5=Mônica Lanzoni |last6=Solis |first6=Daniel Russ |date=1 January 2013 |title=On the morphology of the digestive system of two Monomorium ant species |journal=Journal of Insect Science |volume=13 |issue=1 |page=70 |doi=10.1673/031.013.7001 |pmc=3835044 |pmid=24224520}}</ref> The ] runs lengthwise through the body. It has three sections, with paired ]s and salivary reservoirs.{{sfn|Gullan|Cranston|2005|pp=70–77}} By moving its mouthparts the insect mixes its food with saliva.<ref name="autogenerated1">{{cite web |title=General Entomology – Digestive and Excretory system |url=http://www.cals.ncsu.edu/course/ent425/library/tutorials/internal_anatomy/digestive.html |publisher=North Carolina State University |access-date=3 May 2009 |archive-url=https://web.archive.org/web/20090523024349/http://www.cals.ncsu.edu/course/ent425/library/tutorials/internal_anatomy/digestive.html |archive-date=23 May 2009 |url-status=live }}</ref><ref name="Duncan1939">{{cite book |last=Duncan |first=Carl D. |title=A Contribution to The Biology of North American Vespine Wasps |publisher=] |location=Stanford |year=1939 |edition=1st |pages=24–29}}</ref> Some insects, like ], expel ]s onto their food to break it down, but most insects digest their food in the gut.{{sfn|Nation|2001|p=31}} The ] is lined with cuticule as protection from tough food. It includes the ], pharynx, and ] which stores food.{{sfn|Gullan|Cranston|2005|p=70}} Digestion starts in the mouth with enzymes in the saliva. Strong muscles in the pharynx pump fluid into the mouth, lubricating the food, and enabling certain insects to feed on blood or from the ] and ] transport vessels of plants.{{sfn|Nation|2001|p=30–31}} Once food leaves the crop, it passes to the ], where the majority of digestion takes place. Microscopic projections, ], increase the surface area of the wall to absorb nutrients.{{sfn|Nation|2001|p=32}} In the ], undigested food particles are joined by ] to form fecal pellets; most of the water is absorbed, leaving a dry pellet to be eliminated. Insects may have one to hundreds of ]. These remove nitrogenous wastes from the hemolymph of the insect and regulate osmotic balance. Wastes and solutes are emptied directly into the alimentary canal, at the junction between the midgut and hindgut.{{sfn|Gullan|Cranston|2005|pp=71–72, 78–80}} | |||
It should be emphasized that there is extensive variation among different ], ], and even ]s in the digestive system of insects <ref>{{Cite journal|last=Bueno|first=Odair Correa|last2=Tanaka|first2=Francisco André Ossamu|last3=de Lima Nogueira|first3=Neusa|last4=Fox|first4=Eduardo Gonçalves Paterson|last5=Rossi|first5=Mônica Lanzoni|last6=Solis|first6=Daniel Russ|date=2013-01-01|title=On the morphology of the digestive system of two Monomorium ant species|url=https://academic.oup.com/jinsectscience/article/13/1/70/1074608|journal=Journal of Insect Science|language=en|volume=13|issue=1|pages=70|doi=10.1673/031.013.7001|pmc=3835044|pmid=24224520}}</ref>. This is the result of extreme adaptations to various lifestyles. The present description focus on a generalized composition of the digestive system of an adult orthopteroid insect, which is considered basal to interpreting particularities of other groups. | |||
==== Reproductive ==== | |||
The main structure of an insect's digestive system is a long enclosed tube called the ], which runs lengthwise through the body. The alimentary canal directs food unidirectionally from the ] to the ]. It has three sections, each of which performs a different process of digestion. In addition to the alimentary canal, insects also have paired salivary glands and salivary reservoirs. These structures usually reside in the thorax, adjacent to the foregut.<ref name="Gullan and Cranston" />{{Rp|70–77}} The ]s (element 30 in numbered diagram) in an insect's mouth produce saliva. The salivary ducts lead from the glands to the reservoirs and then forward through the head to an opening called the salivarium, located behind the hypopharynx. By moving its mouthparts (element 32 in numbered diagram) the insect can mix its food with saliva. The mixture of saliva and food then travels through the salivary tubes into the mouth, where it begins to break down.<ref name="autogenerated1">{{cite web | title=General Entomology – Digestive and Excretory system | url=http://www.cals.ncsu.edu/course/ent425/library/tutorials/internal_anatomy/digestive.html | publisher=NC state University | accessdate=3 May 2009}}</ref><ref name="Duncan1939">{{cite book |last=Duncan |first=Carl D. |title=A Contribution to The Biology of North American Vespine Wasps|publisher=] |location=Stanford|year=1939 |edition= 1st |pages=24–29}}</ref> Some insects, like ], have ]. Insects using extra-oral digestion expel digestive enzymes onto their food to break it down. This strategy allows insects to extract a significant proportion of the available nutrients from the food source.<ref name="Insect Physiology and Biochemistry">{{cite book|last=Nation|first=James L.|title=Insect Physiology and Biochemistry |publisher=CRC Press |year=2001 |edition= 1st |chapter=Digestion |isbn=978-0-8493-1181-9 |chapter-url=https://books.google.com/?id=l3v2tOvz1uQC&pg=PA31}}</ref>{{Rp|31}} The gut is where almost all of insects' digestion takes place. It can be divided into the ], ] and ]. | |||
{{main|Insect reproductive system}} | |||
===== Foregut ===== | |||
], from an insect of the order ]]] | |||
The first section of the alimentary canal is the ] (element 27 in numbered diagram), or stomodaeum. The foregut is lined with a cuticular lining made of ] and ]s as protection from tough food. The foregut includes the ] (mouth), ], ] and ] and ] (any part may be highly modified), which both store food and signify when to continue passing onward to the midgut.<ref name="Gullan and Cranston" />{{Rp|70}} | |||
The ] consist of a pair of ], accessory glands, one or more ]e to store sperm, and ducts connecting these parts. The ovaries are made up of a variable number of egg tubes, ]. Female insects make eggs, receive and store sperm, manipulate sperm from different males, and lay eggs. Accessory glands produce substances to maintain sperm and to protect the eggs. They can produce glue and protective substances for coating eggs, or tough coverings for a batch of eggs called ]e.{{sfn|Resh|Carde||2009|p=880}} | |||
Digestion starts in ] (mouth) as partially chewed food is broken down by saliva from the salivary glands. As the salivary glands produce fluid and ] (mostly ]s), strong muscles in the pharynx pump fluid into the buccal cavity, lubricating the food like the salivarium does, and helping blood feeders, and xylem and phloem feeders. | |||
For males, the reproductive system consists of one or two ], suspended in the body cavity by ]. The testes contain sperm tubes or follicles in a membranous sac. These connect to a duct that leads to the outside. The terminal portion of the duct may be sclerotized to form the ], the ].{{sfn|Resh|Carde|2009|p=885}} | |||
From there, the pharynx passes food to the esophagus, which could be just a simple tube passing it on to the crop and proventriculus, and then onward to the midgut, as in most insects. Alternately, the foregut may expand into a very enlarged crop and proventriculus, or the crop could just be a ], or fluid-filled structure, as in some Diptera species.<ref name="Insect Physiology and Biochemistry" />{{Rp|30–31}} | |||
==== Respiratory ==== | |||
] defecating. Note the contraction of the ] to provide internal pressure]] | |||
{{main|Respiratory system of insects}} | |||
===== Midgut ===== | |||
Once food leaves the crop, it passes to the ] (element 13 in numbered diagram), also known as the mesenteron, where the majority of digestion takes place. Microscopic projections from the midgut wall, called ], increase the surface area of the wall and allow more nutrients to be absorbed; they tend to be close to the origin of the midgut. In some insects, the role of the microvilli and where they are located may vary. For example, specialized microvilli producing digestive enzymes may more likely be near the end of the midgut, and absorption near the origin or beginning of the midgut.<ref name="Insect Physiology and Biochemistry" />{{Rp|32}} | |||
]'' extends horizontally across the body, interlinked with the diamond-shaped ] (also green) and surrounded by ] (red). Blue depicts ].]] | |||
===== Hindgut ===== | |||
In the ] (element 16 in numbered diagram), or proctodaeum, undigested food particles are joined by ] to form fecal pellets. The rectum absorbs 90% of the water in these fecal pellets, and the dry pellet is then eliminated through the anus (element 17), completing the process of digestion. Envaginations at the anterior end of the hindgut form the Malpighian tubules, which form the main excretory system of insects. | |||
] is accomplished without ]s. Instead, insects have a system of internal tubes and sacs through which gases either diffuse or are actively pumped, delivering oxygen directly to tissues that need it via their ] and tracheoles. In most insects, air is taken in through paired ]s, openings on the sides of the abdomen and thorax. The respiratory system limits the size of insects. As insects get larger, ] via spiracles becomes less efficient, and thus the heaviest insect currently weighs less than 100 g. However, with increased atmospheric oxygen levels, as were present in the late ], larger insects were possible, such as dragonflies with wingspans of more than {{Convert |2 |ft |cm |sigfig=1 |spell=in}}.<ref>{{cite web|title=What Keeps Bugs from Being Bigger?|date=8 August 2007|publisher=Argonne National Laboratory|url=https://www1.aps.anl.gov/APS-Science-Highlight/2007/What-Keeps-Bugs-from-Being-Bigger|archive-url=https://web.archive.org/web/20170514060330/https://www1.aps.anl.gov/APS-Science-Highlight/2007/What-Keeps-Bugs-from-Being-Bigger |archive-date=14 May 2017|access-date=15 July 2013}}</ref> Gas exchange patterns in insects range from continuous and ] ventilation, to ].{{sfn|Gullan|Cranston|2005|pp=65–68}}<ref name="IPE">{{cite book |last1=Chown |first1=S. L. |last2=Nicholson |first2=S. W. |title=Insect Physiological Ecology |publisher=] |year=2004 |location=New York |isbn=978-0-19-851549-4}}</ref><ref name="aquins"/><ref>{{cite book |last1=Merritt |first1=R. W. |last2=Cummins |first2=K. W. |last3=Berg |first3=M. B. |title=An Introduction To The Aquatic Insects Of North America |year=2007 |publisher=Kendall Hunt Publishing |isbn=978-0-7575-4128-5}}</ref> | |||
==== Excretory system ==== | |||
Insects may have one to hundreds of ] (element 20). These tubules remove nitrogenous wastes from the hemolymph of the insect and regulate osmotic balance. Wastes and solutes are emptied directly into the alimentary canal, at the junction between the midgut and hindgut.<ref name="Gullan and Cranston" />{{Rp|71–72, 78–80}} | |||
==== |
==== Circulatory ==== | ||
{{main|Insect reproductive system}} | |||
The reproductive system of female insects consist of a pair of ], accessory glands, one or more ]e, and ducts connecting these parts. The ovaries are made up of a number of egg tubes, called ], which vary in size and number by species. The number of eggs that the insect is able to make vary by the number of ovarioles with the rate that eggs can develop being also influenced by ovariole design. Female insects are able make eggs, receive and store sperm, manipulate sperm from different males, and lay eggs. Accessory glands or glandular parts of the oviducts produce a variety of substances for sperm maintenance, transport and fertilization, as well as for protection of eggs. They can produce glue and protective substances for coating eggs or tough coverings for a batch of eggs called ]e. Spermathecae are tubes or sacs in which sperm can be stored between the time of mating and the time an egg is fertilized.<ref name="ReshCarde2009" />{{rp|880}} | |||
{{further|Insect physiology#Circulatory system}} | |||
For males, the reproductive system is the ], suspended in the body cavity by ] and the fat body. Most male insects have a pair of testes, inside of which are sperm tubes or follicles that are enclosed within a membranous sac. The follicles connect to the vas deferens by the vas efferens, and the two tubular vasa deferentia connect to a median ejaculatory duct that leads to the outside. A portion of the vas deferens is often enlarged to form the seminal vesicle, which stores the sperm before they are discharged into the female. The seminal vesicles have glandular linings that secrete nutrients for nourishment and maintenance of the sperm. The ejaculatory duct is derived from an invagination of the epidermal cells during development and, as a result, has a cuticular lining. The terminal portion of the ejaculatory duct may be sclerotized to form the intromittent organ, the aedeagus. The remainder of the male reproductive system is derived from embryonic mesoderm, except for the germ cells, or ], which descend from the primordial pole cells very early during embryogenesis.<ref name="ReshCarde2009" />{{rp|885}} | |||
Because oxygen is delivered directly to tissues via tracheoles, the circulatory system is not used to carry oxygen, and is therefore greatly reduced. The insect circulatory system is open; it has no ]s or ], and instead consists of little more than a single, perforated dorsal tube that pulses ]. This dorsal blood vessel is divided into two sections: the heart and aorta. The dorsal blood vessel circulates the ], arthropods' fluid analog of ], from the rear of the body cavity forward.{{sfn|Gullan|Cranston|2005|pp=61–65}}<ref>{{cite web |url=http://www.cals.ncsu.edu/course/ent425/tutorial/circulatory.html |title=Circulatory System |last=Meyer|first=John R. |date=17 February 2006 |publisher=Department of Entomology, NC State University |location=NC State University |page=1 |archive-url=https://web.archive.org/web/20090927000720/http://www.cals.ncsu.edu/course/ent425/tutorial/circulatory.html |archive-date=27 September 2009 |url-status=dead |access-date=11 October 2009 |df=dmy-all}}</ref> Hemolymph is composed of plasma in which ] are suspended. Nutrients, hormones, wastes, and other substances are transported throughout the insect body in the hemolymph. Hemocytes include many types of cells that are important for immune responses, wound healing, and other functions. Hemolymph pressure may be increased by muscle contractions or by swallowing air into the digestive system to aid in molting.<ref>{{cite book |last1=Triplehorn |first1=Charles |title=Borror and DeLong's introduction to the study of insects |publisher=Thompson Brooks/Cole |others=Johnson, Norman F., Borror, Donald J. |year=2005 |isbn=978-0030968358 |edition=7th |location=Belmont, California |pages=27–28 |oclc=55793895 }}</ref> | |||
==== Respiratory system ==== | |||
]'' extends horizontally across the body, interlinked with the diamond-shaped ] (also green) and surrounded by ] (red). Blue depicts ].]] | |||
] is accomplished without ]s. Instead, the ] uses a system of internal tubes and sacs through which gases either diffuse or are actively pumped, delivering oxygen directly to tissues that need it via their ] (element 8 in numbered diagram). In most insects, air is taken in through openings on the sides of the abdomen and thorax called ]s. | |||
==== Sensory ==== | |||
The respiratory system is an important factor that limits the size of insects. As insects get larger, this type of oxygen transport is less efficient and thus the heaviest insect currently weighs less than 100 g. However, with increased atmospheric oxygen levels, as were present in the late ], larger insects were possible, such as dragonflies with wingspans of more than two feet.<ref>{{cite web|title=What Keeps Bugs from Being Bigger?|date=8 August 2007|publisher=Argonne National Laboratory|url=https://www1.aps.anl.gov/APS-Science-Highlight/2007/What-Keeps-Bugs-from-Being-Bigger|archive-url=https://web.archive.org/web/20170514060330/https://www1.aps.anl.gov/APS-Science-Highlight/2007/What-Keeps-Bugs-from-Being-Bigger |archive-date=14 May 2017|accessdate=15 July 2013}}</ref> | |||
{{further|Insect physiology#Sensory organs}} | |||
There are many different patterns of ] demonstrated by different groups of insects. Gas exchange patterns in insects can range from continuous and ] ventilation, to ].<ref name="Gullan and Cranston" />{{Rp|65–68}} During continuous gas exchange, ] is taken in and ] is released in a continuous cycle. In discontinuous gas exchange, however, the insect takes in oxygen while it is active and small amounts of carbon dioxide are released when the insect is at rest.<ref name="IPE">{{cite book | last = Chown | first = S.L. |author2=S.W. Nicholson | title = Insect Physiological Ecology | publisher = Oxford University Press | year = 2004 | location = New York|isbn=978-0-19-851549-4}}</ref> Diffusive ventilation is simply a form of continuous gas exchange that occurs by ] rather than physically taking in the oxygen. Some species of insect that are submerged also have adaptations to aid in respiration. As larvae, many insects have gills that can extract oxygen dissolved in water, while others need to rise to the water surface to replenish air supplies, which may be held or trapped in special structures.<ref name="aquins" /><ref>{{cite book|author1=Merritt, RW |author2=KW Cummins |author3=MB Berg |last-author-amp=yes |title=An Introduction To The Aquatic Insects Of North America|year=2007|publisher=Kendall Hunt Publishing Company|isbn=978-0-7575-4128-5}}</ref> | |||
]s and other sensory organs such as antennae able to detect movements and chemical stimuli on their heads.]] | |||
==== Circulatory system ==== | |||
Because oxygen is delivered directly to tissues via tracheoles, the circulatory system is not used to carry oxygen, and is therefore greatly reduced. The insect circulatory system is open; it has no ]s or ], and instead consists of little more than a single, perforated dorsal tube that pulses ]. This dorsal blood vessel (element 14) is divided into two sections: the heart and aorta. The dorsal blood vessel circulates the ], arthropods' fluid analog of ], from the rear of the body cavity forward.<ref name="Gullan and Cranston" />{{Rp|61–65}}<ref>{{cite web|url=http://www.cals.ncsu.edu/course/ent425/tutorial/circulatory.html|title=Circulatory System|last=Meyer|first=John R.|date=17 February 2006|publisher=Department of Entomology, NC State University|location=NC State University|page=1|archiveurl=https://web.archive.org/web/20090927000720/http://www.cals.ncsu.edu/course/ent425/tutorial/circulatory.html|archivedate=27 September 2009|deadurl=yes|accessdate=11 October 2009|df=dmy-all}}</ref> Hemolymph is composed of plasma in which ] are suspended. Nutrients, hormones, wastes, and other substances are transported throughout the insect body in the hemolymph. Hemocytes include many types of cells that are important for immune responses, wound healing, and other functions. Hemolymph pressure may be increased by muscle contractions or by swallowing air into the digestive system to aid in moulting.<ref>{{Cite book|title=Borror and DeLong's introduction to the study of insects|last=Triplehorn|first=Charles|publisher=Thompson Brooks/Cole|others=Johnson, Norman F., Borror, Donald J.|year=2005|isbn=978-0030968358|edition= 7th|location=Belmont, CA|pages=27–28|oclc=55793895}}</ref> Hemolymph is also a major part of the open ] of other ], such as ] and ].<ref>{{cite book|url=|title=The Insects; Structure and Function|last=Chapman|first=R. F.|date=1998|publisher=Cambridge University Press|isbn=978-0521578905|edition= 4th|series=|volume=|location=Cambridge, UK|pages=|doi=|jfm=|mr=|zbl=|id=}}</ref><ref>{{Cite journal|last1=Wyatt|first1=G.R.|year=1961|title=The Biochemistry of Insect Hemolymph|journal=Annual Review of Entomology|volume=6|pages=75–102|doi=10.1146/annurev.en.06.010161.000451|pmc=|pmid=}}</ref> | |||
Many insects possess numerous specialized ] able to detect stimuli including limb position (]) by ], light, ], chemicals (senses of ] and ]), sound, and heat.{{sfn|Gullan|Cranston|2014|pp=95–124}} Some insects such as ] can perceive ] wavelengths, or detect ], while the ] of male moths can detect the ]s of female moths over distances of over a kilometer.<ref>{{cite web |url=http://crazydaz.com/insects.pdf |title=Insects |publisher=Alien Life Forms |page=4 |access-date=17 May 2009 |archive-url=https://web.archive.org/web/20110708201217/http://crazydaz.com/insects.pdf |archive-date=8 July 2011 |url-status=live}}</ref> There is a trade-off between visual acuity and chemical or tactile acuity, such that most insects with well-developed eyes have reduced or simple antennae, and vice versa. Insects perceive sound by different mechanisms, such as thin vibrating membranes (]).{{sfn|Gullan|Cranston|2014|pp=97–103}} Insects were the earliest organisms to produce and sense sounds. Hearing has evolved independently at least 19 times in different insect groups.<ref name="Warren Nowotny 2021">{{Cite journal |first1=Ben |last1=Warren |first2=Manuela |last2=Nowotny |title=Bridging the Gap Between Mammal and Insect Ears – A Comparative and Evolutionary View of Sound-Reception |date=11 April 2021 |journal=Frontiers in Ecology and Evolution |volume=9 |doi=10.3389/fevo.2021.667218 |doi-access=free }}</ref> | |||
Most insects, except some ], are able to perceive light and dark. Many have acute vision capable of detecting small and rapid movements. The eyes may include simple eyes or ] as well as larger ]s. Many species can detect light in the ], ] and ] wavelengths, with color vision. Phylogenetic analysis suggests that UV-green-blue ] existed from at least the ] period, some 400 million years ago.<ref name="insvision">{{cite journal |last1=Briscoe |first1=A. D. |last2=Chittka |first2=L. |title=The evolution of color vision in insects |year=2001 |journal=Annual Review of Entomology |volume=46 |pages=471–510 |doi=10.1146/annurev.ento.46.1.471 |pmid=11112177 |s2cid=20894534 }}</ref> | |||
The individual lenses in compound eyes are immobile, but fruit flies have photoreceptor cells underneath each lens which move rapidly in and out of focus, in a series of movements called photoreceptor microsaccades. This gives them, and possibly many other insects, a much clearer image of the world than previously assumed.<ref>{{Cite journal |title=Binocular mirror–symmetric microsaccadic sampling enables Drosophila hyperacute 3D vision |first1=Joni |last1=Kemppainen |first2=Ben |last2=Scales |first3=Keivan |last3=Razban Haghighi |first4=Jouni |last4=Takalo |first5=Neveen |last5=Mansour |first6=James |last6=McManus |first7=Gabor|last7=Leko |first8=Paulus |last8=Saari |first9=James |last9=Hurcomb |first10=Andra |last10=Antohi |first11=Jussi-Petteri |last11=Suuronen |first12=Florence |last12=Blanchard |first13=Roger C.|last13=Hardie |first14=Zhuoyi |last14=Song |first15=Mark |last15=Hampton |first16=Marina |last16=Eckermann |first17=Fabian |last17=Westermeier |first18=Jasper |last18=Frohn |first19=Hugo |last19=Hoekstra |first20=Chi-Hon |last20=Lee |first21=Marko |last21=Huttula |first22=Rajmund |last22=Mokso |first23=Mikko |last23=Juusola |display-authors=5 |date=22 March 2022 |journal=Proceedings of the National Academy of Sciences |volume=119 |issue=12 |pages=e2109717119 |doi=10.1073/pnas.2109717119 |doi-access=free |pmid=35298337 |pmc=8944591 |bibcode=2022PNAS..11909717K }}</ref> | |||
An insect's ] is via ], usually on the antennae and the mouthparts. These detect both airborne ] and odorants on surfaces, including pheromones from other insects and compounds released by food plants. Insects use olfaction to locate mating partners, food, and places to lay eggs, and to avoid predators. It is thus an extremely important sense, enabling insects to discriminate between thousands of volatile compounds.<ref name="Carraher Dalziel Jordan 2015">{{Cite journal |last1=Carraher |first1=Colm |last2=Dalziel |first2=Julie |last3=Jordan |first3=Melissa D. |last4=Christie |first4=David L. |last5=Newcomb |first5=Richard D. |last6=Kralicek |first6=Andrew V. |title=Towards an understanding of the structural basis for insect olfaction by odorant receptors |journal=Insect Biochemistry and Molecular Biology |volume=66 |pages=31–41 |doi=10.1016/j.ibmb.2015.09.010 |year=2015 |pmid=26416146|bibcode=2015IBMB...66...31C |url=https://figshare.com/articles/journal_contribution/22745009 }}</ref> | |||
Some insects are capable of ]; ants and bees navigate using it both locally (near their nests) and when migrating.<ref name="Wajnberg 2010">{{cite journal |last1=Wajnberg |first1=E. |author2=Acosta-Avalos, D. |author3=Alves, O.C. |author4=de Oliveira, J.F. |author5=Srygley, R.B. |author6=Esquivel, D.M. |year=2010 |title=Magnetoreception in eusocial insects: An update |journal=] |volume=7 |issue=Suppl 2 |pages=S207–S225 |doi=10.1098/rsif.2009.0526.focus |pmid=20106876 |pmc=2843992}}</ref> The ] detects magnetic fields using the hair-like ] on its antennae.<ref name="Esquivel 2005">{{cite journal |last1=Esquivel |first1=Darci M.S. |last2=Wajnberg |first2=E. |last3=do Nascimento |first3=F.S. |last4=Pinho |first4=M.B. |last5=Lins de Barros |first5=H.G.P. |last6=Eizemberg |first6=R. |year=2005 |title=Do Magnetic Storms Change Behavior of the Stingless Bee Guiriçu (''Schwarziana quadripunctata'')? |journal=] |volume=94 |issue=2 |pages=139–142 |doi=10.1007/s00114-006-0169-z |pmid=17028885|s2cid=10746883 }}</ref><ref name="Lucano 2005">{{cite journal |last1=Lucano |first1=M.J. |last2=Cernicchiaro |first2=G. |last3=Wajnberg |first3=E. |last4=Esquivel |first4=D.M.S. |year=2005 |title=Stingless Bee Antennae: A Magnetic Sensory Organ? |journal=] |volume=19 |issue=3 |pages=295–300 |doi=10.1007/s10534-005-0520-4 |pmid=16799867 |s2cid=10162385 }}</ref> | |||
== Reproduction and development == | == Reproduction and development == | ||
{{multiple image | |||
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| image1 = Hoverflies mating midair.jpg | |||
| alt1 = | |||
| caption1 =A pair of '']'' hoverflies mating in flight. | |||
| image2 =MatingGrasshopper.jpg | |||
| alt2 = | |||
| caption2 =A pair of '']'' mating. | |||
}} | |||
=== Life-cycles === | |||
The majority of insects hatch from ]. The fertilization and development takes place inside the egg, enclosed by a shell (]) that consists of maternal tissue. In contrast to eggs of other arthropods, most insect eggs are drought resistant. This is because inside the chorion two additional membranes develop from embryonic tissue, the ] and the ]. This serosa secretes a ] rich in ] that protects the embryo against desiccation. In ] however the serosa does not develop, but these flies lay their eggs in damp places, such as rotting matter.<ref>{{cite journal|last1= Jacobs|first1= C.G.|last2= Rezende|first2= G.L.|last3= Lamers|first3= G.E.|last4= van der Zee|first4= M.|year= 2013|title= The extraembryonic serosa protects the insect egg against desiccation|journal= Proceedings of the Royal Society of London B|volume= 280|issue= 1764|page= 20131082|pmid= 23782888|doi=10.1098/rspb.2013.1082|pmc= 3712428}}</ref> Some species of insects, like the cockroach '']'', as well as juvenile aphids and tsetse flies, are ]. The eggs of ovoviviparous animals develop entirely inside the female, and then hatch immediately upon being laid.<ref name="mcgraw-hill" /> Some other species, such as those in the genus of cockroaches known as '']'', are ], and thus ] inside the mother and are ].<ref name="Gullan and Cranston" />{{Rp|129, 131, 134–135}} Some insects, like parasitic wasps, show ], where a single fertilized egg divides into many and in some cases thousands of separate embryos.<ref name="Gullan and Cranston" />{{Rp|136–137}} Insects may be ''univoltine'', ''bivoltine'' or ''multivoltine'', i.e. they may have one, two or many broods (generations) in a year.<ref name="OdonateGlossary">{{cite web|title=Glossary of Lepidopteran and Odonate anatomy|url=http://www.vararespecies.org/glossary.shtml|website=Rare species atlas|publisher=Virginia Department of Conservation and Recreation|year=2013|accessdate=14 June 2013}}</ref> | |||
] mating ]] | |||
] ''Orgyia recens'' is an example of ] in insects.]] | |||
Other developmental and reproductive variations include ], ], ] or ], ], ] and more rarely ].<ref name="Gullan and Cranston" />{{Rp|143}} In haplodiploidy, which is a type of ], the offspring's sex is determined by the number of sets of ]s an individual receives. This system is typical in bees and wasps.<ref>{{cite journal |author1=Hughes, William O. H. |author2=Oldroyd, Benjamin P. |author3=Beekman, Madeleine |author4=Ratnieks, Francis L. W. | title = Ancestral Monogamy Shows Kin Selection Is Key to the Evolution of Eusociality| journal = ]| volume = 320| issue = 5880| pages = 1213–1216|date=2008 |pmid=18511689 |doi=10.1126/science.1156108|bibcode = 2008Sci...320.1213H}}</ref> Polymorphism is where a species may have different ''morphs'' or ''forms'', as in the ], which has four different varieties: green, pink and yellow or tan. Some insects may retain ]s that are normally only seen in juveniles; this is called paedomorphosis. In peramorphosis, an opposite sort of phenomenon, insects take on previously unseen traits after they have matured into adults. Many insects display sexual dimorphism, in which males and females have notably different appearances, such as the moth '']'' as an exemplar of sexual dimorphism in insects. | |||
The majority of insects hatch from ]. The fertilization and development takes place inside the egg, enclosed by a shell (]) that consists of maternal tissue. In contrast to eggs of other arthropods, most insect eggs are drought resistant. This is because inside the chorion two additional membranes develop from embryonic tissue, the ] and the ]. This serosa secretes a ] rich in ] that protects the embryo against desiccation.<ref>{{cite journal |last1=Jacobs |first1=C. G. |last2=Rezende |first2=G. L. |last3=Lamers |first3=G. E. |last4=van der Zee |first4=M. |year=2013 |title=The extraembryonic serosa protects the insect egg against desiccation |journal=Proceedings of the Royal Society of London B |volume=280 |issue=1764 |page=20131082 |pmid=23782888 |doi=10.1098/rspb.2013.1082 |pmc=3712428 }}</ref> Some species of insects, like aphids and tsetse flies, are ]: their eggs develop entirely inside the female, and then hatch immediately upon being laid.<ref name="mcgraw-hill">"insect physiology" ''McGraw-Hill Encyclopedia of Science and Technology'', Ch. 9, p. 233, 2007</ref> Some other species, such as in the cockroach genus '']'', are ], ] inside the mother and ].{{sfn|Gullan|Cranston|2005|pp=129, 131, 134–135}} Some insects, like ]s, are ], meaning that a single fertilized egg divides into many separate embryos.{{sfn|Gullan|Cranston|2005|pp=136–137}} Insects may be ], bivoltine or multivoltine, having one, two or many broods in a year.<ref name="OdonateGlossary">{{cite web |title=Glossary of Lepidopteran and Odonate anatomy |url=http://www.vararespecies.org/glossary.shtml |website=Rare species atlas |publisher=Virginia Department of Conservation and Recreation |year=2013 |access-date=14 June 2013 |archive-url=https://web.archive.org/web/20131004213832/http://www.vararespecies.org/glossary.shtml |archive-date=4 October 2013|url-status=live }}</ref> | |||
Some insects use ], a process in which the female can reproduce and give birth without having the eggs ] by a ]. Many aphids undergo a form of parthenogenesis, called cyclical parthenogenesis, in which they alternate between one or many generations of asexual and sexual reproduction.<ref>{{cite journal|title=Effect of nitrogen fertilization on ''Aphis gossypii'' (Homoptera: Aphididae): variation in size, color, and reproduction|author1=Nevo, E. |author2=Coll, M. |journal=Journal of Economic Entomology |volume=94|issue= 1 |pages= 27–32|year= 2001|pmid= 11233124 |doi=10.1603/0022-0493-94.1.27}}</ref><ref>{{cite journal |url=http://docserver.esa.catchword.org/deliver/cw/pdf/esa/freepdfs/0046225x/v34n4s26.pdf |archive-url=http://webarchive.nationalarchives.gov.uk/20100909141631/http%3A//docserver.esa.catchword.org/deliver/cw/pdf/esa/freepdfs/0046225x/v34n4s26.pdf |dead-url=yes |archive-date=2010-09-09 |title=Effect of nitrogen fertilizer on the intrinsic rate of increase of the rusty plum aphid, ''Hysteroneura setariae'' (Thomas) (Homoptera: Aphididae) on rice (''Oryza sativa'' L.) |author1=Jahn, G.C. |author2=Almazan, L.P. |author3=Pacia, J. |journal=Environmental Entomology |volume=34 |issue=4 |pages=938–943 |year=2005 |doi=10.1603/0046-225X-34.4.938 }}</ref> In summer, aphids are generally female and parthenogenetic; in the autumn, males may be produced for sexual reproduction. Other insects produced by parthenogenesis are bees, wasps and ants, in which they spawn males. However, overall, most individuals are female, which are produced by fertilization. The males are ] and the females are ].<ref name="mcgraw-hill" /> More rarely, some insects display ], in which a given individual has both male and female reproductive organs. | |||
] giving birth to live female young by ] from unfertilized eggs]] | |||
Insect life-histories show adaptations to withstand cold and dry conditions. Some temperate region insects are capable of activity during winter, while some others migrate to a warmer climate or go into a state of ].<ref>{{cite web |url=http://insects.about.com/od/adaptations/p/wintersurvival.htm |title=Where do insects go in winter? |author=Debbie Hadley |publisher=] |accessdate=19 April 2012}}</ref> Still other insects have evolved mechanisms of ] that allow eggs or pupae to survive these conditions.<ref>{{cite journal|title=Insect Cold-Hardiness: To Freeze or Not to Freeze|author=Lee, Richard E Jr.|journal=BioScience|volume=39|issue=5|year=1989 |pages=308–313|url=http://www.units.muohio.edu/cryolab/publications/documents/Lee89_BioSci.pdf|doi=10.2307/1311113|jstor=1311113}}</ref> | |||
] deposits an egg before flying off.]] | |||
Other developmental and reproductive variations include ], ], ] or ], ], parthenogenesis, and more rarely ].{{sfn|Gullan|Cranston|2005|p=143}}<ref>{{Cite book |last=Judson |first=Olivia |url=https://books.google.com/books?id=HzzdYcX9P54C&pg=PA198 |title=Dr. Tatiana's Sex Advice to All Creation: The Definitive Guide to the Evolutionary Biology of Sex |date=2002-08-14 |publisher=Macmillan |isbn=978-0-8050-6331-8 |page=198}}</ref> In ], which is a type of ], the offspring's sex is determined by the number of sets of ]s an individual receives. This system is typical in bees and wasps.<ref>{{cite journal |author1=Hughes, William O. H. |author2=Oldroyd, Benjamin P. |author3=Beekman, Madeleine |author4=Ratnieks, Francis L. W. |title=Ancestral Monogamy Shows Kin Selection Is Key to the Evolution of Eusociality|journal=] |volume=320 |issue=5880 |pages=1213–1216 |date=2008 |pmid=18511689 |doi=10.1126/science.1156108 |bibcode=2008Sci...320.1213H |s2cid=20388889 }}</ref> | |||
Some insects are ], meaning that the female can reproduce and give birth without having the eggs ] by a ]. Many aphids undergo a cyclical form of parthenogenesis in which they alternate between one or many generations of asexual and sexual reproduction.<ref>{{cite journal |last1=Nevo |first1=E. |last2=Coll |first2=M. |title=Effect of nitrogen fertilization on ''Aphis gossypii'' (Homoptera: Aphididae): variation in size, color, and reproduction |journal=Journal of Economic Entomology |volume=94 |issue=1 |pages=27–32 |year=2001 |pmid= 11233124 |doi=10.1603/0022-0493-94.1.27 |s2cid=25758038 |doi-access=free }}</ref><ref>{{cite journal |last1=Jahn |first1=G. C. |author2=Almazan, L .P. |author3=Pacia, J. |title=Effect of nitrogen fertilizer on the intrinsic rate of increase of the rusty plum aphid, ''Hysteroneura setariae'' (Thomas) (Homoptera: Aphididae) on rice (''Oryza sativa'' L.) |url=http://docserver.esa.catchword.org/deliver/cw/pdf/esa/freepdfs/0046225x/v34n4s26.pdf |archive-url=http://webarchive.nationalarchives.gov.uk/20100909141631/http%3A//docserver.esa.catchword.org/deliver/cw/pdf/esa/freepdfs/0046225x/v34n4s26.pdf |url-status=dead |archive-date=2010-09-09 |journal=Environmental Entomology |volume=34 |issue=4 |pages=938–943 |year=2005 |doi=10.1603/0046-225X-34.4.938 |s2cid=1941852 }}</ref> In summer, aphids are generally female and parthenogenetic; in the autumn, males may be produced for sexual reproduction. Other insects produced by parthenogenesis are bees, wasps and ants; in their ] system, ] females spawn many females and a few ] males.<ref name="mcgraw-hill"/> | |||
=== Metamorphosis === | === Metamorphosis === | ||
] in insects is the biological process of development all insects must undergo. There are two forms of metamorphosis: incomplete metamorphosis and complete metamorphosis. | |||
] in insects is the process of development that converts young to adults. There are two forms of metamorphosis: incomplete and complete. | |||
==== Incomplete metamorphosis ==== | |||
==== Incomplete ==== | |||
{{Main|Hemimetabolism}} | {{Main|Hemimetabolism}} | ||
] in a ] with multiple ]s. Egg is not shown. The largest specimen is adult.]] | |||
] insects, those with incomplete metamorphosis, change gradually by undergoing a series of ]. An insect molts when it outgrows its exoskeleton, which does not stretch and would otherwise restrict the insect's growth. The molting process begins as the insect's ] secretes a new ] inside the old one. After this new epicuticle is secreted, the epidermis releases a mixture of enzymes that digests the endocuticle and thus detaches the old cuticle. When this stage is complete, the insect makes its body swell by taking in a large quantity of water or air, which makes the old cuticle split along predefined weaknesses where the old exocuticle was thinnest.<ref name="Gullan and Cranston" />{{Rp|142}}<ref name="RuppertFoxBarnes2004P523To524">{{cite book |author1=Ruppert, E.E. |author2=Fox, R.S. |author3=Barnes, R.D. |last-author-amp=yes | title=Invertebrate Zoology | publisher=Brooks / Cole | edition= 7th | isbn=978-0-03-025982-1 | year=2004 | pages=523–524}}</ref> | |||
] insects, those with incomplete metamorphosis, change gradually after hatching from the ] by undergoing a series of ] through stages called ]s, until the final, ], stage is reached. An insect molts when it outgrows its exoskeleton, which does not stretch and would otherwise restrict the insect's growth. The molting process begins as the insect's ] secretes a new ] inside the old one. After this new epicuticle is secreted, the epidermis releases a mixture of enzymes that digests the endocuticle and thus detaches the old cuticle. When this stage is complete, the insect makes its body swell by taking in a large quantity of water or air; this makes the old cuticle split along predefined weaknesses where it was thinnest.{{sfn|Gullan|Cranston|2005|p=142}}<ref name="RuppertFoxBarnes2004P523To524">{{cite book |author1=Ruppert, E. E. |author2=Fox, R. S. |author3=Barnes, R. D. |title=Invertebrate Zoology |publisher=Brooks / Cole |edition=7th |isbn=978-0-03-025982-1 |year=2004 |pages= |url=https://archive.org/details/isbn_9780030259821/page/523 }}</ref> | |||
Immature insects that go through incomplete metamorphosis are called ] or in the case of dragonflies and damselflies, also ]. Nymphs are similar in form to the adult except for the presence of wings, which are not developed until adulthood. With each molt, nymphs grow larger and become more similar in appearance to adult insects. | |||
{{wide image|Aeshna cyanea freshly slipped L2.jpg | 2000px| This ] dragonfly ]s its exoskeleton several times during its life as a ]; shown is the final molt to become a winged adult (]).}} | |||
==== Complete ==== | |||
==== Complete metamorphosis ==== | |||
{{Main|Holometabolism}} | {{Main|Holometabolism}} | ||
] life cycle, an example of ].]] | |||
], or complete metamorphosis, is where the insect changes in four stages, an ] or ], a ], a ] and the ] or ]. In these species, an egg hatches to produce a ], which is generally worm-like in form. This worm-like form can be one of several varieties: eruciform (caterpillar-like), scarabaeiform (grub-like), campodeiform (elongated, flattened and active), elateriform (wireworm-like) or vermiform (maggot-like). The larva grows and eventually becomes a ], a stage marked by reduced movement and often sealed within a ]. There are three types of pupae: obtect, exarate or coarctate. Obtect pupae are compact, with the legs and other appendages enclosed. Exarate pupae have their legs and other appendages free and extended. Coarctate pupae develop inside the larval skin.<ref name="Gullan and Cranston" />{{Rp|151}} Insects undergo considerable change in form during the pupal stage, and emerge as adults. Butterflies are a well-known example of insects that undergo complete metamorphosis, although most insects use this life cycle. Some insects have evolved this system to ]. | |||
] from egg through ] larvae to ] and adult]] | |||
Complete metamorphosis is a trait of the most diverse insect group, the ].<ref name="Gullan and Cranston" />{{Rp|143}} Endopterygota includes 11 Orders, the largest being ] (flies), ] (butterflies and moths), and ] (bees, wasps, and ants), and ] (beetles). This form of development is exclusive to insects and not seen in any other arthropods. | |||
], or complete metamorphosis, is where the insect changes in four stages, an egg or ], a ], a ] and the adult or ]. In these species, an egg hatches to produce a larva, which is generally worm-like in form. This can be eruciform (caterpillar-like), scarabaeiform (grub-like), campodeiform (elongated, flattened and active), elateriform (wireworm-like) or vermiform (maggot-like). The larva grows and eventually becomes a pupa, a stage marked by reduced movement. There are three ]: obtect, exarate or coarctate. Obtect pupae are compact, with the legs and other appendages enclosed. Exarate pupae have their legs and other appendages free and extended. Coarctate pupae develop inside the larval skin.{{sfn|Gullan|Cranston|2005|p=151}} Insects undergo considerable change in form during the pupal stage, and emerge as adults. Butterflies are well-known for undergoing complete metamorphosis; most insects use this life cycle. Some insects have evolved this system to ]. Complete metamorphosis is a trait of the most diverse insect group, the ].{{sfn|Gullan|Cranston|2005|p=143}} | |||
== Senses and communication == | |||
Many insects possess very sensitive and specialized organs of ]. Some insects such as ] can perceive ] wavelengths, or detect ], while the ] of male moths can detect the ]s of female moths over distances of many kilometers.<ref>{{cite web|url=http://crazydaz.com/insects.pdf |title=Insects|publisher=Alien Life Forms|page=4|accessdate=17 May 2009}}</ref> The yellow paper wasp ('']'') is known for its wagging movements as a form of communication within the colony; it can waggle with a frequency of 10.6±2.1 Hz (n=190). These wagging movements can signal the arrival of new material into the nest and aggression between workers can be used to stimulate others to increase foraging expeditions.<ref>{{cite journal | last1 = Esch | first1 = Harald | year = 1971 | title = Wagging Movements in the Wasp ''Polistes versicolor'' Vulgaris Bequaert | url = | journal = Zeitschrift für Vergleichende Physiologie | volume = 72 | issue = 3| pages = 221–225 | doi=10.1007/bf00297781}}</ref> There is a pronounced tendency for there to be a trade-off between visual acuity and chemical or tactile acuity, such that most insects with well-developed eyes have reduced or simple antennae, and vice versa. There are a variety of different mechanisms by which insects perceive sound; while the patterns are not universal, insects can generally hear sound if they can produce it. Different insect species can have varying ], though most insects can hear only a narrow range of frequencies related to the frequency of the sounds they can produce. Mosquitoes have been found to hear up to 2 kHz, and some grasshoppers can hear up to 50 kHz.<ref>{{cite journal | last=Cator | first=L.J. | date= 2009| title=Harmonic convergence in the love songs of the dengue vector mosquito | journal=Science | volume=323 | issue=5917 | pages=1077–1079 | doi=10.1126/science.1166541 | pmc=2847473 | pmid=19131593 | last2=Arthur | first2=B.J. | last3=Harrington | first3=L.C. | last4=Hoy | first4=R.R. |bibcode = 2009Sci...323.1077C}}</ref> Certain predatory and parasitic insects can detect the characteristic sounds made by their prey or hosts, respectively. For instance, some nocturnal moths can perceive the ] emissions of ]s, which helps them avoid predation.<ref name="Gullan and Cranston" />{{Rp|87–94}} Insects that feed on blood have special sensory structures that can detect ] emissions, and use them to home in on their hosts. | |||
== Communication == | |||
Some insects display a rudimentary ],<ref>{{cite book|last=Möller|first=R. |title=A Biorobotics Approach to the Study of Insect Visual Homing Strategies|year=2002|page=11|url=http://www.ti.uni-bielefeld.de/downloads/publications/habil.pdf|language=German}}</ref> such as the solitary wasps that prey upon a single species. The mother wasp lays her eggs in individual cells and provides each egg with a number of live caterpillars on which the young feed when hatched. Some species of wasp always provide five, others twelve, and others as high as twenty-four caterpillars per cell. The number of caterpillars is different among species, but always the same for each sex of larva. The male solitary wasp in the genus '']'' is smaller than the female, so the mother of one species supplies him with only five caterpillars; the larger female receives ten caterpillars in her cell. | |||
Insects that produce sound can generally hear it. Most ] only a ] of ] related to the frequency of the sounds they can produce. Mosquitoes can hear up to 2 ].<ref>{{cite journal |last1=Cator |first1=L.J. |date= 2009|title=Harmonic convergence in the love songs of the dengue vector mosquito |journal=Science |volume=323 |issue=5917 |pages=1077–1079 |doi=10.1126/science.1166541 |pmc=2847473 |pmid=19131593 |last2=Arthur |first2=B.J. |last3=Harrington |first3=L.C. |last4=Hoy |first4=R.R. |bibcode=2009Sci...323.1077C}}</ref> Certain predatory and parasitic insects can detect the characteristic sounds made by their prey or hosts, respectively. Likewise, some nocturnal moths can perceive the ] emissions of ]s, which helps them ].{{sfn|Gullan|Cranston|2005|pp=87–94}} | |||
=== Light production and vision === | |||
] | |||
A few insects, such as members of the families Poduridae and Onychiuridae (Collembola), ] (Diptera) and the beetle families ], ], ] and ] are ]. The most familiar group are the ], beetles of the family Lampyridae. Some species are able to control this light generation to produce flashes. The function varies with some species using them to attract mates, while others use them to lure prey. Cave dwelling larvae of '']'' (Mycetophilidae, fungus gnats) glow to lure small flying insects into sticky strands of silk.<ref>{{cite journal | title=Literature review of the New Zealand glowworm ''Arachnocampa luminosa'' (Diptera: Keroplatidae) and related cave-dwelling Diptera | last=Pugsley | first=Chris W. | journal=New Zealand Entomologist | year=1983 | volume=7 | issue=4 | pages=419–424 | url=http://www.ento.org.nz/nzentomologist/free_issues/NZEnto07_4_1983/Volume%207-4-419-424.pdf | archive-url=https://web.archive.org/web/20071020094802/http://www.ento.org.nz/nzentomologist/free_issues/NZEnto07_4_1983/Volume%207-4-419-424.pdf | dead-url=yes | archive-date=2007-10-20 | doi=10.1080/00779962.1983.9722435}}</ref> | |||
Some fireflies of the genus '']'' ] the flashing of female '']'' species to attract males of that species, which are then captured and devoured.<ref>{{cite journal|title=Occurrence of Aggressive Mimicry in Fireflies|first=James E.|last=Lloyd|journal=The Florida Entomologist | volume=67 | issue=3 | year=1984 | pages=368–376 | doi=10.2307/3494715 | jstor=3494715}}</ref> The colors of emitted light vary from dull blue (''Orfelia fultoni'', Mycetophilidae) to the familiar greens and the rare reds (''Phrixothrix tiemanni'', Phengodidae).<ref>{{cite book | first=James E. | last=Lloyd |author2=Erin C. Gentry | title=The Encyclopedia of Insects| pages=115–120 | year=2003 | publisher=Academic Press | isbn=978-0-12-586990-4}}</ref> | |||
=== Light production === | |||
Most insects, except some species of ], are able to perceive light and dark. Many species have acute vision capable of detecting minute movements. The eyes may include simple eyes or ] as well as ]s of varying sizes. Many species are able to detect light in the infrared, ultraviolet and the ] wavelengths. Color vision has been demonstrated in many species and phylogenetic analysis suggests that UV-green-blue ] existed from at least the ] period between 416 and 359 million years ago.<ref name="insvision">{{cite journal|title=The evolution of color vision in insects |author1=Briscoe, AD |author2=Chittka, L | year=2001 | journal=Annual Review of Entomology | volume=46 | pages=471–510 | doi=10.1146/annurev.ento.46.1.471|pmid=11112177}}</ref> | |||
A few insects, such as ] (Diptera) and the beetle families ], ], ] and ] are ]. The most familiar group are the ], beetles of the family Lampyridae. Some species are able to control this light generation to produce flashes. The function varies with some species using them to attract mates, while others use them to lure prey. Cave dwelling larvae of '']'' (Mycetophilidae, fungus gnats) glow to lure small flying insects into sticky strands of silk.<ref>{{cite journal |last=Pugsley |first=Chris W. |title=Literature review of the New Zealand glowworm ''Arachnocampa luminosa'' (Diptera: Keroplatidae) and related cave-dwelling Diptera |journal=New Zealand Entomologist |year=1983 |volume=7 |issue=4 |pages=419–424 |url=http://www.ento.org.nz/nzentomologist/free_issues/NZEnto07_4_1983/Volume%207-4-419-424.pdf |archive-url=https://web.archive.org/web/20071020094802/http://www.ento.org.nz/nzentomologist/free_issues/NZEnto07_4_1983/Volume%207-4-419-424.pdf |url-status=dead |archive-date=2007-10-20 |doi=10.1080/00779962.1983.9722435|bibcode=1983NZEnt...7..419P }}</ref> Some fireflies of the genus '']'' ] the flashing of female '']'' species to attract males of that species, which are then captured and devoured.<ref>{{cite journal |first=James E. |last=Lloyd |title=Occurrence of Aggressive Mimicry in Fireflies |journal=The Florida Entomologist |volume=67 |issue=3 |year=1984 |pages=368–376 |doi=10.2307/3494715 |jstor=3494715 |s2cid=86502129}}</ref> The colors of emitted light vary from dull blue (''Orfelia fultoni'', Mycetophilidae) to the familiar greens and the rare reds (''Phrixothrix tiemanni'', Phengodidae).<ref>{{cite book |first1=James E. |last1=Lloyd |last2=Gentry |first2=Erin C. |title=The Encyclopedia of Insects |pages= |year=2003 |publisher=Academic Press |isbn=978-0-12-586990-4 |url=https://archive.org/details/encyclopediaofin00bada/page/115 }}</ref> | |||
=== Sound production and hearing === | |||
Insects were the earliest organisms to produce and sense sounds. Insects make sounds mostly by mechanical action of appendages. In ]s and crickets, this is achieved by ]. ]s make the loudest sounds among the insects by producing and amplifying sounds with special modifications to their body to form ]s and associated musculature. The African ] '']'' has been measured at 106.7 ]s at a distance of {{convert|50|cm|in|abbr=on}}.<ref name="walker">Walker, T.J., ed. (2001). .</ref> Some insects, such as the '']'' moths, ]s and ] butterflies, can hear ] and take evasive action when they sense that they have been detected by bats.<ref>{{cite journal|author=Kay, Robert E. |title=Acoustic signalling and its possible relationship to assembling and navigation in the moth, ''Heliothis zea''|journal= Journal of Insect Physiology |volume=15|issue=6 |year=1969|pages= 989–1001 |doi=10.1016/0022-1910(69)90139-5}}</ref><ref>{{cite journal|author=Spangler, Hayward G. |title=Moth hearing, defense, and communication|journal= Annual Review of Entomology |volume=33|issue=1 |year=1988|pages= 59–81 |doi=10.1146/annurev.ento.33.1.59}}</ref> Some moths produce ultrasonic clicks that were once thought to have a role in jamming bat ]. The ultrasonic clicks were subsequently found to be produced mostly by unpalatable moths to warn bats, just as ] are used against predators that hunt by sight.<ref>{{cite journal | last=Hristov | first=N.I. |author2=Conner, W.E. | year=2005 | title=Sound strategy: acoustic aposematism in the bat–tiger moth arms race | journal=Naturwissenschaften | volume=92 | pages=164–169 | doi=10.1007/s00114-005-0611-7 | pmid=15772807 | issue=4|bibcode = 2005NW.....92..164H}}</ref> Some otherwise palatable moths have evolved to ] these calls.<ref>{{cite journal | last=Barber | first=J.R. |author2=W.E. Conner | year=2007 | title=Acoustic mimicry in a predator–prey interaction | journal=Proceedings of the National Academy of Sciences | volume=104 | issue=22 | pages=9331–9334 | doi=10.1073/pnas.0703627104|pmid=17517637 | pmc=1890494|bibcode = 2007PNAS..104.9331B}}</ref> More recently, the claim that some moths can jam bat sonar has been revisited. Ultrasonic recording and high-speed infrared videography of bat-moth interactions suggest the palatable tiger moth really does defend against attacking big brown bats using ultrasonic clicks that jam bat sonar.<ref>{{cite journal | last=Corcoran | first=Aaron J. |author2=Jesse R. Barber | author3= William E. Conner | year=2009 | title=Tiger Moth Jams Bat Sonar | journal=Science | volume=325 | issue=5938 |pages=325–327 | doi=10.1126/science.1174096 |bibcode = 2009Sci...325..325C | pmid=19608920}}</ref> | |||
=== Sound production === | |||
{{Listen | filename=Grasshoppers.ogg | title=Grasshopper stridulation | description=Several unidentified grasshoppers stridulating | format=] | pos=left}} | |||
Very low sounds are also produced in various species of ], ], ], ] and ]. These low sounds are simply the sounds made by the insect's movement. Through microscopic stridulatory structures located on the insect's muscles and joints, the normal sounds of the insect moving are amplified and can be used to warn or communicate with other insects. Most sound-making insects also have ]s that can perceive airborne sounds. Some species in ], such as the ] (water boatmen), are known to communicate via underwater sounds.<ref>{{cite journal|last=Theiss|first=Joachim|year=1982|title=Generation and radiation of sound by stridulating water insects as exemplified by the corixids|journal=Behavioral Ecology and Sociobiology|volume=10|pages=225–235|doi=10.1007/BF00299689|issue=3}}</ref> Most insects are also able to sense ]s transmitted through surfaces. | |||
] | |||
Communication using surface-borne vibrational signals is more widespread among insects because of size constraints in producing air-borne sounds.<ref>{{cite journal | last=Virant-Doberlet | first=M. |author2=Čokl A. | year=2004 | title=Vibrational communication in insects | journal=Neotropical Entomology | volume=33 | issue=2 | pages=121–134| doi=10.1590/S1519-566X2004000200001}}</ref> Insects cannot effectively produce low-frequency sounds, and high-frequency sounds tend to disperse more in a dense environment (such as ]), so insects living in such environments communicate primarily using substrate-borne vibrations.<ref>{{cite journal | last=Bennet-Clark | first=H.C. | year=1998 | title=Size and scale effects as constraints in insect sound communication | journal=Philosophical Transactions of the Royal Society of London. Series B, Biological Sciences | volume=353 | pages=407–419 | doi=10.1098/rstb.1998.0219 | issue=1367| pmc=1692226 }}</ref> The mechanisms of production of vibrational signals are just as diverse as those for producing sound in insects. | |||
Insects make sounds mostly by mechanical action of appendages. In ]s and crickets, this is achieved by ]. ]s make the loudest sounds among the insects by producing and amplifying sounds with special modifications to their body to form ]s and associated musculature. The African ] '']'' has been measured at 106.7 ]s at a distance of {{convert|50|cm|in|abbr=on}}.<ref name="walker">{{Cite web |title=The University of Florida Book of Insect Records|publisher=Department of Entomology & Nematology, UF/IFAS |url=https://entnemdept.ufl.edu/walker/ufbir/index.shtml |access-date=2022-01-13 |website=entnemdept.ufl.edu }}</ref> Some insects, such as the '']'' moths, ]s and ] butterflies, can hear ] and ] when they sense that they have been detected by bats.<ref>{{cite journal |last=Kay |first=Robert E. |title=Acoustic signalling and its possible relationship to assembling and navigation in the moth, ''Heliothis zea''|journal= Journal of Insect Physiology |volume=15 |issue=6 |year=1969|pages= 989–1001 |doi=10.1016/0022-1910(69)90139-5|bibcode=1969JInsP..15..989K }}</ref><ref>{{cite journal |last=Spangler |first=Hayward G. |title=Moth hearing, defense, and communication|journal= Annual Review of Entomology |volume=33 |issue=1 |year=1988 |pages=59–81 |doi=10.1146/annurev.ento.33.1.59}}</ref> Some moths produce ultrasonic clicks that warn predatory bats of their unpalatability (acoustic ]),<ref>{{cite journal |last1=Hristov |first1=N. I. |last2=Conner |first2=William E. |year=2005 |title=Sound strategy: acoustic aposematism in the bat–tiger moth arms race |journal=Naturwissenschaften |volume=92 |pages=164–169 |doi=10.1007/s00114-005-0611-7 |pmid=15772807 |issue=4 |bibcode=2005NW.....92..164H |s2cid=18306198 }}</ref> while some palatable moths have evolved to mimic these calls (acoustic ]).<ref>{{cite journal |last1=Barber |first1=J. R. |last2=Conner |first2=W. E. |year=2007 |title=Acoustic mimicry in a predator–prey interaction |journal=Proceedings of the National Academy of Sciences |volume=104 |issue=22 |pages=9331–9334 |doi=10.1073/pnas.0703627104|pmid=17517637 |pmc=1890494 |bibcode=2007PNAS..104.9331B |doi-access=free }}</ref> The claim that some moths can ] has been revisited. Ultrasonic recording and high-speed infrared videography of bat-moth interactions suggest the palatable tiger moth really does defend against attacking big brown bats using ultrasonic clicks that jam bat sonar.<ref>{{cite journal |last=Corcoran |first=Aaron J. |author2=Barber, Jesse R. |last3=Conner |first3=William E. |year=2009 |title=Tiger Moth Jams Bat Sonar |journal=Science |volume=325 |issue=5938 |pages=325–327 |doi=10.1126/science.1174096 |bibcode=2009Sci...325..325C |pmid=19608920 |s2cid=206520028 }}</ref> | |||
Some species use vibrations for communicating within members of the same species, such as to attract mates as in the songs of the ] '']''.<ref>{{cite journal | journal=Journal of Insect Behavior | title=The Influence of Substrate on Male Responsiveness to the Female Calling Song in ''Nezara viridula'' | volume=14 | issue=3 | pages=313–332 | year=2001 |first1=Nadège |last1=Miklas |author2=Stritih, Nataša |author3=Čokl, Andrej |author4=Virant-Doberlet, Meta |author5=Renou, Michel |doi=10.1023/A:1011115111592}}</ref> Vibrations can also be used to communicate between entirely different species; ] (gossamer-winged butterfly) caterpillars, which are ] (living in a mutualistic association with ants) communicate with ants in this way.<ref>{{cite journal | last=DeVries | first=P.J. | year=1990 | title=Enhancement of symbiosis between butterfly caterpillars and ants by vibrational communication | journal=Science | volume=248 | pages=1104–1106 |doi=10.1126/science.248.4959.1104 | pmid=17733373 | issue=4959|bibcode = 1990Sci...248.1104D}}</ref> The ] has the ability to press air through its spiracles to make a hissing noise as a sign of aggression;<ref>{{cite journal|last=Nelson|first=Margaret C.|author2=Jean Fraser|year=1980|title=Sound production in the cockroach, Gromphadorhina portentosa: evidence for communication by hissing|journal=Behavioral Ecology and Sociobiology|volume=6|issue=4|pages=305–314|doi=10.1007/BF00292773}}</ref> the ] makes a squeaking noise by forcing air out of their pharynx when agitated, which may also reduce aggressive worker honey bee behavior when the two are in close proximity.<ref>{{cite journal |last1=Moritz |first1=R.F.A. |last2=Kirchner |first2=W.H. |last3=Crewe |first3=R.M. |date=1991 |title=Chemical camouflage of the death's head hawkmoth (Acherontia atropos L.) in honeybee colonies |journal=Naturwissenschaften |volume=78 |issue=4 |doi=10.1007/BF01136209 |bibcode=1991NW.....78..179M |pages=179–182}}</ref> | |||
{{Listen |filename=Grasshoppers.ogg |title=Grasshopper stridulation |description=Several unidentified grasshoppers stridulating |format=] |pos=right}} | |||
Very low sounds are produced in various species of ], ], ], ] and ]. These low sounds are produced by the insect's movement, amplified by stridulatory structures on the insect's muscles and joints; these sounds can be used to warn or communicate with other insects. Most sound-making insects also have ]s that can perceive airborne sounds. Some ]ns, such as the ], communicate via underwater sounds.<ref>{{cite journal |last=Theiss |first=Joachim |year=1982 |title=Generation and radiation of sound by stridulating water insects as exemplified by the corixids |journal=Behavioral Ecology and Sociobiology |volume=10 |pages=225–235 |doi=10.1007/BF00299689 |issue=3 |bibcode=1982BEcoS..10..225T |s2cid=10338592}}</ref> | |||
] | |||
Communication using surface-borne vibrational signals is more widespread among insects because of size constraints in producing air-borne sounds.<ref>{{cite journal |last1=Virant-Doberlet |first1=M. |last2=Čokl |first2=Andrej |year=2004 |title=Vibrational communication in insects |journal=Neotropical Entomology |volume=33 |issue=2 |pages=121–134|doi=10.1590/S1519-566X2004000200001 |doi-access=free }}</ref> Insects cannot effectively produce low-frequency sounds, and high-frequency sounds tend to disperse more in a dense environment (such as ]), so insects living in such environments communicate primarily using substrate-borne vibrations.<ref>{{cite journal |last=Bennet-Clark |first=H. C. |year=1998 |title=Size and scale effects as constraints in insect sound communication |journal=Philosophical Transactions of the Royal Society of London. Series B, Biological Sciences |volume=353 |pages=407–419 |doi=10.1098/rstb.1998.0219 |issue=1367 |pmc=1692226 }}</ref> | |||
Some species use vibrations for communicating, such as to attract mates as in the songs of the ] '']''.<ref>{{cite journal |journal=Journal of Insect Behavior |title=The Influence of Substrate on Male Responsiveness to the Female Calling Song in ''Nezara viridula'' |volume=14 |issue=3 |pages=313–332 |year=2001 |first1=Nadège |last1=Miklas |author2=Stritih, Nataša |author3=Čokl, Andrej |author4=Virant-Doberlet, Meta |author5=Renou, Michel |doi=10.1023/A:1011115111592|bibcode=2001JIBeh..14..313M |s2cid=11369425 }}</ref> Vibrations can also be used to communicate between species; ] caterpillars, which ] communicate with ants in this way.<ref>{{cite journal |last=DeVries |first=P. J. |year=1990 |title=Enhancement of symbiosis between butterfly caterpillars and ants by vibrational communication |journal=Science |volume=248 |pages=1104–1106 |doi=10.1126/science.248.4959.1104 |pmid=17733373 |issue=4959|bibcode=1990Sci...248.1104D |s2cid=35812411 }}</ref> The ] has the ability to press air through its spiracles to make a hissing noise as a sign of aggression;<ref>{{cite journal |last=Nelson |first=Margaret C. |author2=Fraser, Jean |year=1980 |title=Sound production in the cockroach, Gromphadorhina portentosa: evidence for communication by hissing |journal=Behavioral Ecology and Sociobiology |volume=6 |issue=4 |pages=305–314 |doi=10.1007/BF00292773 |bibcode=1980BEcoS...6..305N |s2cid=9637568 }}</ref> the ] makes a squeaking noise by forcing air out of their pharynx when agitated, which may also reduce aggressive worker honey bee behavior when the two are close.<ref>{{cite journal |last1=Moritz |first1=R. F. A. |last2=Kirchner |first2=W. H. |last3=Crewe |first3=R. M. |date=1991 |title=Chemical camouflage of the death's head hawkmoth (Acherontia atropos L.) in honeybee colonies |journal=Naturwissenschaften |volume=78 |issue=4 |doi=10.1007/BF01136209 |bibcode=1991NW.....78..179M |pages=179–182 |s2cid=45597312 }}</ref> | |||
=== Chemical communication === | === Chemical communication === | ||
Chemical communications in animals rely on a variety of aspects including taste and smell. Chemoreception is the physiological response of a sense organ (i.e. taste or smell) to a chemical stimulus where the chemicals act as signals to regulate the state or activity of a cell. A semiochemical is a message-carrying chemical that is meant to attract, repel, and convey information. Types of semiochemicals include pheromones and kairomones. One example is the butterfly ''] ''which uses chemical signals as a form of mimicry to aid in predation.<ref name="Corruption">{{cite journal |last1=Thomas |first1=Jeremy |last2=Schönrogge |first2=Karsten |last3=Bonelli |first3=Simona |last4=Barbero |first4=Francesca |last5=Balletto |first5=Emilio |title=Corruption of ant acoustical signals by mimetic social parasites |journal=Communicative and Integrative Biology |date=2010 |volume=3 |issue=2 |pages=169–171 |pmid=20585513 |pmc=2889977 |doi=10.4161/cib.3.2.10603}}</ref> | |||
{{main |Chemical communication in insects |Insect olfaction}} | |||
In addition to the use of sound for communication, a wide range of insects have evolved ]. These chemicals, termed ]s, are often derived from plant metabolites include those meant to attract, repel and provide other kinds of information. ]s, a type of semiochemical, are used for attracting mates of the opposite sex, for aggregating ] individuals of both sexes, for deterring other individuals from approaching, to mark a trail, and to trigger aggression in nearby individuals. ]s benefit their producer by the effect they have upon the receiver. ]s benefit their receiver instead of their producer. Synomones benefit the producer and the receiver. While some chemicals are targeted at individuals of the same species, others are used for communication across species. The use of scents is especially well known to have developed in social insects.<ref name="Gullan and Cranston" />{{Rp|96–105}} | |||
] glands, producing different ]s for ].{{sfn |Gullan |Cranston |2005 |pp=96–105}}]] | |||
Many insects have evolved ]. These ]s are often derived from plant metabolites including those meant to attract, repel and provide other kinds of information. ]s are used for attracting mates of the opposite sex, for aggregating ] individuals of both sexes, for deterring other individuals from approaching, to mark a trail, and to trigger aggression in nearby individuals. ]s benefit their producer by the effect they have upon the receiver. ]s benefit their receiver instead of their producer. Synomones benefit the producer and the receiver. While some chemicals are targeted at individuals of the same species, others are used for communication across species. The use of scents is especially well-developed in social insects.{{sfn |Gullan |Cranston |2005 |pp=96–105}} {{visible anchor |Cuticular hydrocarbons |Cuticular hydrocarbon}} are nonstructural materials produced and secreted to the cuticle surface to fight ] and ]s. They are important, too, as pheromones, especially in social insects.<ref name="Yan-Liebig-2021">{{cite journal |last1=Yan |first1=Hua |last2=Liebig |first2=Jürgen |title=Genetic basis of chemical communication in eusocial insects |journal=] |publisher=] & ] |volume=35 |issue=7–8 |date=1 April 2021 |doi=10.1101/gad.346965.120 |pages=470–482 |pmid=33861721 |pmc=8015721 }}</ref> | |||
== Social behavior == | == Social behavior == | ||
]).]] | |||
]s, such as ]s, ]s and many ]s and ]s, are the most familiar species of ] animals.<ref>{{cite web|title= Social insects|last=Brewer|first=Gary|url=http://www.ndsu.nodak.edu/entomology/topics/societies.htm|publisher=North Dakota State University|accessdate=6 May 2009 |archiveurl = https://web.archive.org/web/20080321171246/http://www.ndsu.nodak.edu/entomology/topics/societies.htm |archivedate = 21 March 2008}}</ref> They live together in large well-organized colonies that may be so tightly integrated and genetically similar that the colonies of some species are sometimes considered ]s. It is sometimes argued that the various species of ] are the only invertebrates (and indeed one of the few non-human groups) to have evolved a system of abstract symbolic communication where a behavior is used to ''represent'' and convey specific information about something in the environment. In this communication system, called ], the angle at which a bee dances represents a direction relative to the sun, and the length of the dance represents the distance to be flown.<ref name="Gullan and Cranston" />{{Rp|309–311}} Though perhaps not as advanced as honey bees, ]s also potentially have some social communication behaviors. '']'', for example, exhibit a faster learning curve for visiting unfamiliar, yet rewarding flowers, when they can see a conspecific foraging on the same species.<ref>{{cite journal |author1=Leadbeater, E. |author2=L. Chittka | year = 2007 | title = The dynamics of social learning in an insect model, the bumblebee (''Bombus terrestris'') | journal = Behavioral Ecology and Sociobiology | volume = 61 | issue = 11 | pages = 1789–1796 | doi=10.1007/s00265-007-0412-4}}</ref> | |||
{{main|Eusociality}} | |||
Only insects that live in nests or colonies demonstrate any true capacity for fine-scale spatial orientation or homing. This can allow an insect to return unerringly to a single hole a few millimeters in diameter among thousands of apparently identical holes clustered together, after a trip of up to several kilometers' distance. In a phenomenon known as ], insects that ] have shown the ability to recall a specific location up to a year after last viewing the area of interest.<ref>{{cite journal|last=Salt|first=R.W.|date=1961|title=Principles of Insect Cold-Hardiness|journal=Annual Review of Entomology|doi=10.1146/annurev.en.06.010161.000415 |volume=6 |pages=55–74}}</ref> A few insects seasonally ] large distances between different geographic regions (e.g., the overwintering areas of the ]).<ref name="Gullan and Cranston" />{{Rp|14}} | |||
{{multiple image | |||
|total_width=300 | |||
|image1=Termite Cathedral DSC03570.jpg | |||
|caption1=A ] created by ] ]. | |||
|image2=Bee waggle dance.png | |||
|caption2=]'s figure-eight ]. An orientation 45° to the right of ‘up' on the comb indicates food 45° to the right of the sun. The dancer's rapid waggling blurs her abdomen. | |||
}} | |||
]s, such as ]s, ]s and many ]s and ]s, are ].<ref>{{cite web |title=Social insects |last=Brewer |first=Gary |url=http://www.ndsu.nodak.edu/entomology/topics/societies.htm |publisher=North Dakota State University |access-date=6 May 2009 |archive-url=https://web.archive.org/web/20080321171246/http://www.ndsu.nodak.edu/entomology/topics/societies.htm |archive-date=21 March 2008}}</ref> They live together in such large well-organized colonies of genetically similar individuals that they are sometimes considered ]s. In particular, reproduction is largely limited to a ]; other females are ], prevented from reproducing by ]. ]s have evolved a system of abstract symbolic communication where a behavior is used to represent and convey specific information about the environment. In this communication system, called ], the angle at which a bee dances represents a direction relative to the sun, and the length of the dance represents the distance to be flown.{{sfn|Gullan|Cranston|2005|pp=309–311}} ]s too have some social communication behaviors. '']'', for example, more rapidly learns about visiting unfamiliar, yet rewarding flowers, when they can see a conspecific foraging on the same species.<ref>{{cite journal |author1=Leadbeater, E. |author2=Chittka, L. |year=2007 |title=The dynamics of social learning in an insect model, the bumblebee (''Bombus terrestris'') |journal=Behavioral Ecology and Sociobiology |volume=61 |issue=11 |pages=1789–1796 |doi=10.1007/s00265-007-0412-4 |bibcode=2007BEcoS..61.1789L |s2cid=569654 }}</ref> | |||
Only insects that live in nests or colonies possess fine-scale spatial orientation. Some can ] unerringly to a single hole a few millimeters in diameter among thousands of similar holes, after a trip of several kilometers. In ], insects that ] are able to recall a specific location up to a year after last viewing the area of interest.<ref>{{cite journal |last=Salt |first=R. W. |date=1961 |title=Principles of Insect Cold-Hardiness |journal=Annual Review of Entomology |doi=10.1146/annurev.en.06.010161.000415 |volume=6 |pages=55–74 }}</ref> A few insects seasonally ] large distances between different geographic regions, as in the continent-wide ].{{sfn|Gullan|Cranston|2005|p=14}} | |||
=== Care of young === | === Care of young === | ||
The ] insects build nests, guard eggs, and provide food for offspring full-time (see ]). | |||
Most insects, however, lead short lives as adults, and rarely interact with one another except to mate or compete for mates. A small number |
] insects build nests, guard eggs, and provide food for offspring full-time. Most insects, however, lead short lives as adults, and rarely interact with one another except to mate or compete for mates. A small number provide ], where they at least guard their eggs, and sometimes guard their offspring until adulthood, possibly even feeding them. Many wasps and bees construct a nest or burrow, ] in it, and lay an egg upon those provisions, providing no further care.<ref>{{cite web |title=Social Insects |url=http://www.ndsu.nodak.edu/entomology/topics/societies.htm |publisher=North Dakota State University |access-date=12 October 2009 |archive-url=https://web.archive.org/web/20080321171246/http://www.ndsu.nodak.edu/entomology/topics/societies.htm |archive-date=21 March 2008}}</ref> | ||
== Locomotion == | == Locomotion == | ||
=== Flight === | === Flight === | ||
{{Main|Insect flight|Insect wing}} | |||
] feeding in flight]] | |||
[[File:Motion of Insectwing.gif|right|upright=1.15|thumb|Basic motion of the insect wing in insect with an indirect flight mechanism scheme of dorsoventral cut through a thorax segment with <br /> '''a''' wings <br /> '''b''' joints <br /> | |||
'''c''' dorsoventral muscles <br /> | |||
'''d''' longitudinal muscles.]] | |||
{{main|Insect flight}} | |||
Insects are the only group of ]s to have developed flight. The evolution of insect wings has been a subject of debate. Some ] suggest that the wings are from paranotal lobes, or extensions from the insect's exoskeleton called the ], called the ''paranotal theory''. Other theories are based on a ] origin. These theories include suggestions that wings originated from modified gills, spiracular flaps or as from an appendage of the epicoxa. The ''epicoxal theory'' suggests the insect wings are modified epicoxal exites, a modified appendage at the base of the legs or ].<ref>{{cite journal | title=Hypothesis testing in evolutionary developmental biology: a case study from insect wings | last1=Jockusch | first1=EL | last2=Ober | first2=KA | journal=Journal of Heredity |date=September 2004 | volume=95 | issue=5 | pages=382–396 | doi=10.1093/jhered/esh064 | pmid=15388766}}</ref> In the ] age, some of the '']'' dragonflies had as much as a {{convert|50|cm|in|abbr=on}} wide wingspan. The appearance of gigantic insects has been found to be consistent with high atmospheric oxygen. The respiratory system of insects constrains their size, however the high oxygen in the atmosphere allowed larger sizes.<ref>{{cite journal | last=Dudley | first=R | year=1998 | title=Atmospheric oxygen, giant Paleozoic insects and the evolution of aerial locomotor performance | journal=Journal of Experimental Biology | volume=201 | issue=8 | pages=1043–1050 | url=http://jeb.biologists.org/content/201/8/1043.full.pdf}}</ref> The largest flying insects today are much smaller and include several moth species such as the ] and the white witch ('']''). | |||
] are capable of rapid and agile ]. ]] | |||
Insect flight has been a topic of great interest in ] due partly to the inability of steady-state theories to explain the lift generated by the tiny wings of insects. But insect wings are in motion, with flapping and vibrations, resulting in churning and ], and the misconception that physics says ] persisted throughout most of the twentieth century. | |||
Insects are the only group of ]s to have developed flight. The ancient groups of insects in the Palaeoptera, the dragonflies, damselflies and mayflies, operate their wings directly by paired muscles attached to points on each wing base that raise and lower them. This can only be done at a relatively slow rate. All other insects, the Neoptera, have ], in which the flight muscles cause rapid oscillation of the thorax: there can be more wingbeats than nerve impulses commanding the muscles. One pair of flight muscles is aligned vertically, contracting to pull the top of the thorax down, and the wings up. The other pair runs longitudinally, contracting to force the top of the thorax up and the wings down.<ref name="Chapman">{{cite book |last=Chapman |first=A. D. |year=2006 |title=Numbers of living species in Australia and the World |publisher=Canberra: ] |isbn=978-0-642-56850-2 |url=http://www.deh.gov.au/biodiversity/abrs/publications/other/species-numbers/index.html |archive-url=https://archive.today/20121130101928/http://www.deh.gov.au/biodiversity/abrs/publications/other/species-numbers/index.html |url-status=dead |archive-date=30 November 2012 }}</ref><ref>{{cite journal |last=Smith |first=D. S. |title=Flight muscles of insects |journal=] |volume=212 |pages=76–88 |year=1965 |issue=6 |pmid=14327957 |bibcode=1965SciAm.212f..76S |doi=10.1038/scientificamerican0665-76 }}</ref> Most insects gain ] by creating a spiralling ] at the ] of the wings.<ref name="aerodynamics">{{cite journal |last=Sane |first=Sanjay P. |title=The aerodynamics of insect flight |journal=] |year=2003 |volume=206 |pages=4191–4208 |doi=10.1242/jeb.00663 |pmid=14581590 |issue=23 |s2cid=17453426 |doi-access=free |bibcode=2003JExpB.206.4191S |url=http://www.cs.washington.edu/homes/diorio/MURI2003/Publications/sane_review.pdf}}</ref> Small insects like thrips with tiny feathery wings gain lift using the ] mechanism; the wings are clapped together and pulled apart, flinging vortices into the air at the leading edges and at the wingtips.<ref>{{cite journal |last=Weis-Fogh |first=Torkel |author-link=Torkel Weis-Fogh |date=1973 |title=Quick estimates of flight fitness in hovering animals, including novel mechanisms of lift production |journal=] |volume=59 |issue=1 |pages=169–230 |doi=10.1242/jeb.59.1.169 |bibcode=1973JExpB..59..169W }}</ref><ref>{{Cite journal |last=Bennett |first=L. |date=1977 |title=Clap and fling aerodynamics- an experimental evaluation |journal=] |volume=69 |issue=1 |pages=261–272 |doi=10.1242/jeb.69.1.261 |bibcode=1977JExpB..69..261B }}</ref> | |||
Unlike ]s, many small insects are swept along by the ]<ref>Yates, Diana (2008). ] at Urbana–Champaign. Retrieved on 26 April 2009.</ref> although many of the larger insects are known to make ]. ]s are known to be transported long distances by low-level ]s.<ref>{{cite journal | last=Drake | first=V.A. |author2=R.A. Farrow | year=1988 | title=The Influence of Atmospheric Structure and Motions on Insect Migration | journal=Annual Review of Entomology | volume=33 | pages=183–210 | doi=10.1146/annurev.en.33.010188.001151}}</ref> As such, fine line patterns associated with converging winds within ] imagery, like the ] radar network, often represent large groups of insects.<ref>Bart Geerts and Dave Leon (2003). . ]. Retrieved on 26 April 2009.</ref> | |||
The evolution of ]s has been ]; it has been suggested they came from modified gills, flaps on the spiracles, or an appendage, the epicoxa, at the base of the legs.<ref>{{cite journal |last1=Jockusch |first1=E. L. |last2=Ober |first2=K. A. |title=Hypothesis testing in evolutionary developmental biology: a case study from insect wings |journal=Journal of Heredity |date=September 2004 |volume=95 |issue=5 |pages=382–396 |doi=10.1093/jhered/esh064 |pmid=15388766 |doi-access=free }}</ref> More recently, entomologists have favored evolution of wings from lobes of the ], of the ], or more likely both.<ref>{{cite book |last=Grimaldi |first=David A. |title=The Complete Insect: Anatomy, Physiology, Evolution, and Ecology |url=https://books.google.com/books?id=xGquEAAAQBAJ&dq=insects+wings+notum+pleuron&pg=PA135 |date=2023 |publisher=] |page=135 |isbn=9780691243115}}</ref> | |||
In the ] age, the dragonfly-like '']'' had as much as a {{convert|50|cm|in|abbr=on}} wide wingspan. The appearance of gigantic insects is consistent with high atmospheric oxygen at that time, as the respiratory system of insects constrains their size.<ref>{{cite journal |last=Dudley |first=R. |year=1998 |title=Atmospheric oxygen, giant Paleozoic insects and the evolution of aerial locomotor performance |journal=Journal of Experimental Biology |volume=201 |issue=8 |pages=1043–1050 |doi=10.1242/jeb.201.8.1043 |pmid=9510518 |bibcode=1998JExpB.201.1043D |url=http://jeb.biologists.org/content/201/8/1043.full.pdf |access-date=8 December 2012 |archive-url=https://web.archive.org/web/20130124032600/http://jeb.biologists.org/content/201/8/1043.full.pdf |archive-date=24 January 2013 |url-status=live}}</ref> The largest flying insects today are much smaller, with the largest wingspan belonging to the white witch moth ('']''), at approximately {{convert|28|cm|in|abbr=on}}.<ref name="BIR">{{Cite web|title=Chapter 32: Largest Lepidopteran Wing Span | The University of Florida Book of Insect Records | Department of Entomology & Nematology | UF/IFAS|url=https://entnemdept.ufl.edu/walker/ufbir/chapters/chapter_32.shtml|access-date=2022-01-13|website=entnemdept.ufl.edu}}</ref> | |||
Unlike ]s, small insects are swept along by the ]<ref>{{cite web |last=Yates |first=Diana |title=Birds migrate together at night in dispersed flocks, new study indicates |url=https://news.illinois.edu/view/6367/206246 |access-date=2022-01-13 |website=news.illinois.edu }}</ref> although many larger insects ]. ]s are transported long distances by low-level ]s.<ref>{{cite journal |last=Drake |first=V. A. |author2=Farrow, R. A. |year=1988 |title=The Influence of Atmospheric Structure and Motions on Insect Migration |journal=] |volume=33 |pages=183–210 |doi=10.1146/annurev.en.33.010188.001151 }}</ref> | |||
=== Walking === | === Walking === | ||
] | |||
{{further|Walking#Insects}} | |||
Many adult insects use six legs for walking and have adopted a ] ]. The tripedal gait allows for rapid walking while always having a stable stance and has been studied extensively in ]es and ]s. The legs are used in alternate triangles touching the ground. For the first step, the middle right leg and the front and rear left legs are in contact with the ground and move the insect forward, while the front and rear right leg and the middle left leg are lifted and moved forward to a new position. When they touch the ground to form a new stable triangle the other legs can be lifted and brought forward in turn and so on.<ref name="Locomotion">{{cite book | last=Biewener | first=Andrew A | title=Animal Locomotion | publisher=Oxford University Press | year=2003 | isbn=978-0-19-850022-3}}</ref> The purest form of the tripedal gait is seen in insects moving at high speeds. However, this type of locomotion is not rigid and insects can adapt a variety of gaits. For example, when moving slowly, turning, avoiding obstacles, climbing or slippery surfaces, four (tetrapod) or more feet (wave-gait<ref>{{cite journal |author1=Grabowska, Martyna |author2=Godlewska, Elzbieta |author3=Schmidt, Joachim |author4=Daun-Gruhn, Silvia |title= Quadrupedal gaits in hexapod animals – inter-leg coordination in free-walking adult stick insects |journal= Journal of Experimental Biology | volume=215| issue=24| pages=4255–4266 |year=2012| doi=10.1242/jeb.073643|pmid=22972892 }}</ref>) may be touching the ground. Insects can also adapt their gait to cope with the loss of one or more limbs. | |||
] | |||
Cockroaches are among the fastest insect runners and, at full speed, adopt a bipedal run to reach a high velocity in proportion to their body size. As cockroaches move very quickly, they need to be video recorded at several hundred frames per second to reveal their gait. More sedate locomotion is seen in the stick insects or walking sticks (]). A few insects have evolved to walk on the surface of the water, especially members of the ] family, commonly known as water striders. A few species of ocean-skaters in the genus '']'' even live on the surface of open oceans, a habitat that has few insect species.<ref>{{cite journal |author1=Ikawa, Terumi |author2=Okabe, Hidehiko |author3=Hoshizaki, Sugihiko |author4=Kamikado, Takahiro |author5=Cheng, Lanna |title=Distribution of the oceanic insects ''Halobates'' (Hemiptera: Gerridae) off the south coast of Japan |journal=Entomological Science | volume=7| issue=4| pages= 351–357 |year=2004| doi=10.1111/j.1479-8298.2004.00083.x}}</ref> | |||
Many adult insects use six legs for walking, with an alternating ]. This allows for rapid walking with a stable stance; it has been studied extensively in ]es and ]s. For the first step, the middle right leg and the front and rear left legs are in contact with the ground and move the insect forward, while the front and rear right leg and the middle left leg are lifted and moved forward to a new position. When they touch the ground to form a new stable triangle, the other legs can be lifted and brought forward in turn.<ref name="Locomotion">{{cite book |last=Biewener |first=Andrew A. |title=Animal Locomotion |publisher=] |year=2003 |isbn=978-0-19-850022-3 |pages= }}{{pn|date=July 2022}}</ref> The purest form of the tripedal gait is seen in insects moving at high speeds. However, this type of locomotion is not rigid and insects can adapt a variety of gaits. For example, when moving slowly, turning, avoiding obstacles, climbing or slippery surfaces, four (tetrapodal) or more feet (]) may be touching the ground.<ref>{{cite journal |last1=Grabowska |first1=Martyna |author2=Godlewska, Elzbieta |author3=Schmidt, Joachim |author4=Daun-Gruhn, Silvia |title= Quadrupedal gaits in hexapod animals – inter-leg coordination in free-walking adult stick insects |journal=Journal of Experimental Biology |volume=215 |issue=24 |pages=4255–4266 |year=2012|doi=10.1242/jeb.073643 |pmid=22972892 |doi-access=free }}</ref> Cockroaches are among the fastest insect runners and, at full speed, adopt a bipedal run. More sedate locomotion is seen in the well-]d stick insects (]). A small number of species such as ]s can move on the surface of water; their claws are recessed in a special groove, preventing the claws from piercing the water's surface film.<ref name="aquins"/> The ocean-skaters in the genus '']'' even live on the surface of open oceans, a habitat that has few insect species.<ref>{{cite journal |last1=Ikawa |first1=Terumi |author2=Okabe, Hidehiko |author3=Hoshizaki, Sugihiko |author4=Kamikado, Takahiro |author5=Cheng, Lanna |title=Distribution of the oceanic insects ''Halobates'' (Hemiptera: Gerridae) off the south coast of Japan |journal=Entomological Science |volume=7 |issue=4 |pages=351–357 |year=2004 |doi=10.1111/j.1479-8298.2004.00083.x |s2cid=85017400 |url=https://escholarship.org/uc/item/9r50k828 }}</ref> | |||
==== Use in robotics ==== | |||
{{See also|Robot locomotion|Hexapod (robotics)}} | |||
Insect walking is of particular interest as an alternative form of locomotion in ]s. The study of insects and ]s has a significant impact on possible robotic methods of transport. This may allow new robots to be designed that can traverse ] that robots with ]s may be unable to handle.<ref name="Locomotion" /> | |||
=== Swimming === | === Swimming === | ||
{{Main|Aquatic insects}} | {{Main|Aquatic insects}} | ||
]'' underwater, showing its paddle-like hindleg adaptation]] | |||
A large number of insects live either part or the whole of their lives underwater. In many of the more primitive orders of insect, the immature stages are spent in an aquatic environment. Some groups of insects, like certain ]s, have aquatic adults as well.<ref name="aquins">{{cite book |author1=Richard W. Merritt |author2=Kenneth W. Cummins |author3=Martin B. Berg (editors) |year=2007 | title=An Introduction to the Aquatic Insects of North America | publisher=Kendall Hunt Publishers | isbn=978-0-7575-5049-2 | edition= 4th}}</ref> | |||
] '']'' underwater, showing its paddle-like hindleg adaptation]] | |||
Many of these species have adaptations to help in under-water locomotion. Water beetles and water bugs have legs adapted into paddle-like structures. Dragonfly ] use jet propulsion, forcibly expelling water out of their rectal chamber.<ref>{{cite journal | last=Mill|first=P.J. |author2=R.S. Pickard | year=1975 | title=Jet-propulsion in anisopteran dragonfly larvae | journal=Journal of Comparative Physiology A | volume=97 | issue=4 | pages=329–338 | doi=10.1007/BF00631969}}</ref> Some species like the ]s are capable of walking on the surface of water. They can do this because their claws are not at the tips of the legs as in most insects, but recessed in a special groove further up the leg; this prevents the claws from piercing the water's surface film.<ref name="aquins" /> Other insects such as the ] '']'' are known to emit pygidial gland secretions that reduce surface tension making it possible for them to move on the surface of water by ] (also known by the ] term ''Entspannungsschwimmen'').<ref>{{cite journal | last=Linsenmair | first=K. |author2=Jander R. | year=1976 | title=Das "entspannungsschwimmen" von ''Velia'' and ''Stenus'' | journal=Naturwissenschaften | volume=50 | page=231 | doi=10.1007/BF00639292 | bibcode=1963NW.....50..231L | issue=6| url=https://nbn-resolving.org/urn:nbn:de:bvb:20-opus-44663 }}</ref><ref>{{cite journal|last=Bush |first=J.W.M. |author2=David L. Hu |year=2006 |title=Walking on Water: Biolocomotion at the Interface |journal=Annual Review of Fluid Mechanics |volume=38 |issue=1 |pages=339–369 |url=http://www.cims.nyu.edu/~dhu/Pubweb/Bush_Hu_06.pdf |doi=10.1146/annurev.fluid.38.050304.092157 |bibcode=2006AnRFM..38..339B |deadurl=yes |archiveurl=https://web.archive.org/web/20070710022624/http://www.cims.nyu.edu/~dhu/Pubweb/Bush_Hu_06.pdf |archivedate=10 July 2007}}</ref> | |||
A large number of insects live either part or the whole of their lives underwater. In many of the more primitive orders of insect, the immature stages are aquatic. In some groups, such as ]s, the adults too are aquatic.<ref name="aquins">{{cite book |editor1=Richard W. Merritt |editor2=Kenneth W. Cummins |editor3=Martin B. Berg |year=2007 |title=An Introduction to the Aquatic Insects of North America |publisher=Kendall Hunt Publishers |isbn=978-0-7575-5049-2 |edition=4th}}</ref> | |||
Many of these species are adapted for under-water locomotion. Water beetles and water bugs have legs adapted into paddle-like structures. Dragonfly ] use jet propulsion, forcibly expelling water out of their rectal chamber.<ref>{{cite journal |last=Mill |first=P. J. |author2=Pickard, R. S. |year=1975 |title=Jet-propulsion in anisopteran dragonfly larvae |journal=Journal of Comparative Physiology A |volume=97 |issue=4 |pages=329–338 |doi=10.1007/BF00631969|s2cid=45066664 }}</ref> Other insects such as the ] '']'' emit ] gland ] secretions that reduce surface tension; this enables them to move on the surface of water by ].<ref>{{cite journal |last=Linsenmair |first=K. |author2=Jander, R. |year=1976 |title=Das "entspannungsschwimmen" von ''Velia'' and ''Stenus'' |journal=Naturwissenschaften |volume=50 |page=231 |doi=10.1007/BF00639292 |bibcode=1963NW.....50..231L |issue=6 |s2cid=40832917 |url=https://nbn-resolving.org/urn:nbn:de:bvb:20-opus-44663 }}</ref><ref>{{cite journal |last=Bush |first=J. W. M. |author2=Hu, David L. Hu |year=2006 |title=Walking on Water: Biolocomotion at the Interface |journal=Annual Review of Fluid Mechanics |volume=38 |issue=1 |pages=339–369 |url=http://www.cims.nyu.edu/~dhu/Pubweb/Bush_Hu_06.pdf |doi=10.1146/annurev.fluid.38.050304.092157 |bibcode=2006AnRFM..38..339B |url-status=dead |archive-url=https://web.archive.org/web/20070710022624/http://www.cims.nyu.edu/~dhu/Pubweb/Bush_Hu_06.pdf |archive-date=10 July 2007}}</ref> | |||
== Ecology == | == Ecology == | ||
{{See also|Insect ecology}} | |||
Insect ecology is the scientific study of how insects, individually or as a community, interact with the surrounding ] or ].<ref name="InsectEcology">{{cite book |title=Insect ecology: an ecosystem approach |last=Schowalter |first=Timothy Duane |edition=2nd (illustrated) |year=2006 |publisher=Academic Press |isbn=978-0-12-088772-9 |page=572 |url=https://books.google.com/books?id=3PD6R-AEvwEC}}</ref>{{rp|3}} Insects play one of the most important roles in their ecosystems, which includes many roles, such as soil turning and aeration, dung burial, pest control, pollination and wildlife nutrition. An example is the ]s, which are ]s that feed on dead animals and fallen trees and thereby ] biological materials into forms found useful by other ]s.<ref>{{cite journal | url=http://wordinfo.info/unit/3562?letter=I&spage=3 | title=The Economic Value of Ecological Services Provided by Insects |author1=Losey, John E. |author2=Vaughan, Mace | journal=BioScience |date= 2006 | volume=56 | issue=4 | pages=311–323(13)| doi=10.1641/0006-3568(2006)562.0.CO;2}}</ref> These insects, and others, are responsible for much of the process by which ] is created.<ref name="Gullan and Cranston" />{{Rp|3, 218–228}} | |||
{{main|Insect ecology}} | |||
=== Defense and predation === | |||
{{See also|Defense in insects}} | |||
] (top) appears very similar to the noxious-tasting ] (bottom).<ref name="Ritland & Brower">{{cite journal |last=Ritland |first=D.B. |author2=L.P. Brower |author-link2=Lincoln Brower |year=1991|title=The viceroy butterfly is not a Batesian mimic |journal=] |volume=350 |issue= 6318|pages=497–498 |doi =10.1038/350497a0 |quote=Viceroys are as unpalatable as monarchs, and significantly more unpalatable than queens from representative Florida populations. |bibcode=1991Natur.350..497R}}</ref>]] | |||
Insects are mostly soft bodied, fragile and almost defenseless compared to other, larger lifeforms. The immature stages are small, move slowly or are immobile, and so all stages are exposed to ] and ]. Insects then have a variety of defense strategies to avoid being attacked by predators or ]s. These include ], ], toxicity and active defense.<ref name="Evans126">{{cite book |last=Evans |first=Arthur V. |author2=Charles Bellamy |year=2000 |title=An Inordinate Fondness for Beetles |publisher=] |isbn=978-0-520-22323-3 |url=https://books.google.com/?id=ZZ_hfpMo8oAC&pg=PA31 |ref=refEvans}}</ref> | |||
Insects play many critical roles in ]s, including soil turning and aeration, dung burial, pest control, pollination and wildlife nutrition.{{sfn|Schowalter|2006|pp=3, 572}} For instance, termites modify the environment around their nests, encouraging grass growth;{{sfn|Gullan|Cranston|2014|p=257}} many ]s are ]s; dung beetles ] biological materials into forms useful to other ]s.{{sfn|Gullan|Cranston|2014|pp=261–264}}<ref>{{cite journal |last1=Losey |first1=John E. |last2=Vaughan |first2=Mace |title=The Economic Value of Ecological Services Provided by Insects |journal=BioScience |date=2006 |volume=56 |issue=4 |pages=311–323(13) |doi=10.1641/0006-3568(2006)562.0.CO;2 |url=http://wordinfo.info/unit/3562?letter=I&spage=3 |access-date=8 November 2011 |archive-url=https://web.archive.org/web/20120112041609/http://wordinfo.info/unit/3562?letter=I&spage=3 |archive-date=12 January 2012 |url-status=live |doi-access=free }}</ref> Insects are responsible for much of the process by which ] is created.{{sfn|Gullan|Cranston|2005|pp=3, 218–228}} | |||
] is an important defense strategy, which involves the use of coloration or shape to blend into the surrounding environment.<ref>{{cite web|title = Photos: Masters of Disguise – Amazing Insect Camouflage|url = http://news.nationalgeographic.com/news/2014/03/140321-insects-fossil-camouflage-mimicry-pictures/|accessdate =11 June 2015|date = 2014-03-24}}</ref> This sort of protective coloration is common and widespread among beetle families, especially those that feed on wood or vegetation, such as many of the ]s (family ]) or ]s. In some of these species, sculpturing or various colored scales or hairs cause the beetle to resemble bird dung or other inedible objects. Many of those that live in sandy environments blend in with the coloration of the substrate.<ref name="Evans126" /> Most phasmids are known for effectively replicating the forms of sticks and leaves, and the bodies of some species (such as ''O. macklotti'' and ''Palophus centaurus'') are covered in mossy or ]ous outgrowths that supplement their disguise. Some species have the ability to change color as their surroundings shift (''B. scabrinota'', ''T. californica''). In a further behavioral adaptation to supplement ], a number of species have been noted to perform a rocking motion where the body is swayed from side to side that is thought to reflect the movement of leaves or twigs swaying in the breeze. Another method by which stick insects avoid predation and resemble twigs is by feigning death (]), where the insect enters a motionless state that can be maintained for a long period. The nocturnal feeding habits of adults also aids Phasmatodea in remaining concealed from predators.<ref name="bedford">{{cite journal|last=Bedford|first=Geoffrey O.|title=Biology and Ecology of the Phasmatodea|journal=Annual Review of Entomology|year=1978|volume=23|pages=125–149|doi=10.1146/annurev.en.23.010178.001013}}</ref> | |||
=== Defense === | |||
Another defense that often uses color or shape to deceive potential enemies is mimicry. A number of ]s (family Cerambycidae) bear a striking resemblance to ]s, which helps them avoid predation even though the beetles are in fact harmless.<ref name="Evans126" /> ] and ] ] complexes are commonly found in Lepidoptera. Genetic polymorphism and natural selection give rise to otherwise edible species (the mimic) gaining a survival advantage by resembling inedible species (the model). Such a mimicry complex is referred to as ''Batesian'' and is most commonly known by the mimicry by the ] ] of the inedible ] ]. Later research has discovered that the viceroy is, in fact more toxic than the monarch and this resemblance should be considered as a case of Müllerian mimicry.<ref name="Ritland & Brower" /> In Müllerian mimicry, inedible species, usually within a taxonomic order, find it advantageous to resemble each other so as to reduce the sampling rate by predators who need to learn about the insects' inedibility. Taxa from the toxic genus '']'' form one of the most well known Müllerian complexes.<ref>{{cite journal |author=Meyer, A. |year=2006 |title=Repeating Patterns of Mimicry |journal=] |volume=4 |issue=10 |page=e341 |doi=10.1371/journal.pbio.0040341 |pmid=17048984 |pmc=1617347}}</ref> | |||
{{main|Defense in insects}} | |||
Chemical defense is another important defense found among species of Coleoptera and Lepidoptera, usually being advertised by bright colors, such as the ]. They obtain their toxicity by sequestering the chemicals from the plants they eat into their own tissues. Some Lepidoptera manufacture their own toxins. Predators that eat poisonous butterflies and moths may become sick and vomit violently, learning not to eat those types of species; this is actually the basis of Müllerian mimicry. A predator who has previously eaten a poisonous lepidopteran may avoid other species with similar markings in the future, thus saving many other species as well.<ref name="ANC">{{cite book |last=Kricher |first=John |title=A Neotropical Companion |pages=157–158|chapter=6 |chapter-url=https://books.google.com/?id=Z3pgdvrSmG8C&pg=PA158 |publisher=] |isbn=978-0-691-00974-2 |date =1999}}</ref> Some ]s of the family Carabidae can spray chemicals from their abdomen with great accuracy, to repel predators.<ref name="Evans126" /> | |||
]'', the masked hunter bug ], ]s itself with sand grains to avoid ]s.]] | |||
Insects are mostly small, soft bodied, and fragile compared to larger lifeforms. The immature stages are small, move slowly or are immobile, and so all stages are exposed to ] and ]. Insects accordingly employ multiple ], including ], ], toxicity and active defense.<ref name="Evans126">{{cite book |last1=Evans |first1=Arthur V. |last2=Bellamy |first2=Charles |year=2000 |title=An Inordinate Fondness for Beetles |publisher=] |isbn=978-0-520-22323-3 |url=https://books.google.com/books?id=ZZ_hfpMo8oAC&pg=PA31 |page=31}}</ref> | |||
Many ] to avoid being noticed by their predators or prey.<ref>{{cite web |title=Photos: Masters of Disguise – Amazing Insect Camouflage |url=http://news.nationalgeographic.com/news/2014/03/140321-insects-fossil-camouflage-mimicry-pictures/ |access-date=11 June 2015 |date=2014-03-24 |archive-url=https://web.archive.org/web/20150612201555/http://news.nationalgeographic.com/news/2014/03/140321-insects-fossil-camouflage-mimicry-pictures/ |archive-date=12 June 2015 |url-status=dead}}</ref> It is common among ]s and ]s that feed on wood or vegetation.<ref name="Evans126"/> ]s mimic the forms of sticks and leaves.<ref name="bedford">{{cite journal |last=Bedford |first=Geoffrey O. |title=Biology and Ecology of the Phasmatodea |journal=Annual Review of Entomology |year=1978 |volume=23 |pages=125–149 |doi=10.1146/annurev.en.23.010178.001013 }}</ref> | |||
Many insects use ] to deceive predators into avoiding them. In ], edible species, such as of ] (the mimics), gain a survival advantage by resembling inedible species (the models).<ref name="Evans126"/><ref name="Ritland & Brower">{{cite journal |last1=Ritland |first1=D. B. |last2=Brower |first2=Lincoln P. |author-link2=Lincoln Brower |year=1991 |title=The viceroy butterfly is not a Batesian mimic |journal=] |volume=350 |issue= 6318|pages=497–498 |doi =10.1038/350497a0 |quote=Viceroys are as unpalatable as monarchs, and significantly more unpalatable than queens from representative Florida populations. |bibcode=1991Natur.350..497R|s2cid=28667520 }}</ref> In ], inedible species, such as of wasps and bees, resemble each other so as to reduce the sampling rate by predators who need to learn that those insects are inedible. '']'' butterflies, many of which are toxic, form Müllerian complexes, advertising their inedibility.<ref>{{cite journal |last=Meyer |first=A. |year=2006 |title=Repeating Patterns of Mimicry |journal=] |volume=4 |issue=10 |page=e341 |doi=10.1371/journal.pbio.0040341 |pmid=17048984 |pmc=1617347 |doi-access=free }}</ref> | |||
] is common among Coleoptera and Lepidoptera, usually being advertised by bright warning colors (]), as in the ]. As larvae, they obtain their ] by sequestering chemicals from the plants they eat into their own tissues. Some manufacture their own toxins. Predators that eat poisonous butterflies and moths may vomit violently, learning not to eat insects with similar markings; this is the basis of Müllerian mimicry.<ref name="ANC">{{cite book |last=Kricher |first=John |title=A Neotropical Companion |pages=157–158 |chapter=6 |chapter-url=https://books.google.com/books?id=Z3pgdvrSmG8C&pg=PA158 |publisher=] |isbn=978-0-691-00974-2 |date=1999}}</ref> | |||
Some ]s of the family Carabidae actively defend themselves, spraying chemicals from their abdomen with great accuracy, to repel predators.<ref name="Evans126"/> | |||
=== Pollination === | === Pollination === | ||
{{See also|Pollination}} | |||
{{main|Entomophily}} | |||
] carrying pollen in a ] back to the hive]]Pollination is the ] by which ] is transferred in the reproduction of plants, thereby enabling ] and ]. Most flowering plants require an animal to do the transportation. While other animals are included as pollinators, the majority of pollination is done by insects.<ref name="USFS">{{cite web|url=http://www.fs.fed.us/wildflowers/pollinators/documents/factsheet_pollinator.pdf |publisher=] |title=Pollinator Factsheet |format=PDF |accessdate=19 April 2012 |deadurl=yes |archiveurl=https://web.archive.org/web/20080410135644/http://www.fs.fed.us/wildflowers/pollinators/documents/factsheet_pollinator.pdf |archivedate=10 April 2008}}</ref> Because insects usually receive benefit for the pollination in the form of energy rich nectar it is a grand example of ]. The various flower traits (and combinations thereof) that differentially attract one type of pollinator or another are known as ]s. These arose through complex plant-animal adaptations. Pollinators find flowers through bright colorations, including ultraviolet, and attractant ]. The study of pollination by insects is known as '']''. | |||
] carrying pollen in a ] back to the hive]] | |||
Pollination is the process by which ] is transferred in the reproduction of plants, thereby enabling ] and ].<ref>{{cite encyclopedia |url=https://www.britannica.com/EBchecked/topic/289001/insect |last=Wigglesworth |first=Vincent Brian |author-link=Vincent Wigglesworth |title=Insect |encyclopedia=] online |access-date=19 April 2012 |archive-url=https://web.archive.org/web/20120504183402/https://www.britannica.com/EBchecked/topic/289001/insect |archive-date=4 May 2012 |url-status=live }}</ref> Most flowering plants require an animal to do the transportation. The majority of ].<ref name="USFS">{{cite web|url=http://www.fs.fed.us/wildflowers/pollinators/documents/factsheet_pollinator.pdf |publisher=] |title=Pollinator Factsheet |access-date=19 April 2012 |url-status=dead |archive-url=https://web.archive.org/web/20080410135644/http://www.fs.fed.us/wildflowers/pollinators/documents/factsheet_pollinator.pdf |archive-date=10 April 2008}}</ref> Because insects usually receive benefit for the pollination in the form of energy rich nectar it is a ]. The various flower traits, such as bright colors and ] that ] with their pollinators, have been called ]s, though around one third of flowers cannot be assigned to a single syndrome.<ref name="Ollerton Alarcón Waser Price 2009 pp. 1471–1480">{{cite journal |last1=Ollerton |first1=Jeff |last2=Alarcón |first2=Ruben |last3=Waser |first3=Nickolas M. |last4=Price |first4=Mary V. |last5=Watts |first5=Stella |last6=Cranmer |first6=Louise |last7=Hingston |first7=Andrew |last8=Peter |first8=Craig I. |last9=Rotenberry |first9=John |display-authors=4 |title=A global test of the pollination syndrome hypothesis |journal=Annals of Botany |publisher=Oxford University Press |volume=103 |issue=9 |date=14 February 2009 |doi=10.1093/aob/mcp031 |pages=1471–1480|pmid=19218577 |pmc=2701765 |doi-access=free }}</ref> | |||
=== Parasitism === | === Parasitism === | ||
Many insects are parasites of other insects such as the ] wasps. These insects are known as ]. They can be beneficial due to their devastation of pests that can destroy crops and other resources. Many insects have a parasitic relationship with humans such as the mosquito. These insects are known to spread diseases such as ] and ] and because of such, mosquitoes indirectly cause more deaths of humans than any other animal. | |||
{{further|Parasitism|Parasitoid wasp}} | |||
Many insects are ]. The largest group, with over 100,000 species<ref name="Polaszek Vilhemsen 2023">{{cite journal |last1=Polaszek |first1=Andrew |last2=Vilhemsen |first2=Lars |title=Biodiversity of hymenopteran parasitoids |journal=Current Opinion in Insect Science |date=2023 |volume=56 |page=101026 |doi=10.1016/j.cois.2023.101026 |pmid=36966863 |s2cid=257756440 |doi-access=free |bibcode=2023COIS...5601026P }}</ref> and perhaps over a million,<ref name="Forbes Bagley Beer Hippee 2018">{{cite journal |last1=Forbes |first1=Andrew A. |last2=Bagley |first2=Robin K. |last3=Beer |first3=Marc A. |last4=Hippee |first4=Alaine C. |last5=Widmayer |first5=Heather A. |display-authors=3 |title=Quantifying the unquantifiable: why Hymenoptera, not Coleoptera, is the most speciose animal order |journal=BMC Ecology |volume=18 |issue=1 |date=12 July 2018 |page=21 |doi=10.1186/s12898-018-0176-x|pmid=30001194 |pmc=6042248 |bibcode=2018BMCE...18...21F |doi-access=free }}</ref> consists of a single ] of ]s among the Hymenoptera.<ref name="Zhang Kopylov 2020">{{Cite journal |last1=Zhang |first1=Qi |last2=Kopylov |first2=Dmitry S. |last3=Rasnitsyn |first3=Alexandr P. |last4=Zheng |first4=Yan |last5=Zhang |first5=Haichun |date=November 2020 |editor-last=Smith |editor-first=Andrew |title=Burmorussidae, a new family of parasitic wasps (Insecta, Hymenoptera) from mid-Cretaceous Burmese amber |url=https://onlinelibrary.wiley.com/doi/10.1002/spp2.1312 |journal=Papers in Palaeontology |volume=6 |issue=4|pages=593–603|doi=10.1002/spp2.1312 |bibcode=2020PPal....6..593Z |s2cid=219039881}}</ref> These are parasites of other insects, eventually killing their hosts.<ref name="Polaszek Vilhemsen 2023"/> Some are hyper-parasites, as their hosts are other parasitoid wasps.<ref name="Polaszek Vilhemsen 2023"/><ref>{{Cite journal |last1=Tanaka |first1=S. |last2=Ohsaki |first2=N. |doi=10.1007/s11284-006-0153-2 |title=Behavioral manipulation of host caterpillars by the primary parasitoid wasp Cotesia glomerata (L.) to construct defensive webs against hyperparasitism |journal=Ecological Research |volume=21 |issue=4 |pages=570 |year=2006 |bibcode=2006EcoR...21..570T |s2cid=23457678 }}</ref> Several groups of insects can be considered as either ]s or ];<ref name=Rollinson>{{cite journal |last=Poulin |first=Robert |author-link=Robert Poulin (zoologist) |editor1=Rollinson, D. |editor2=Hay, S. I. |title=The Many Roads to Parasitism: A Tale of Convergence |journal=Advances in Parasitology |url=https://books.google.com/books?id=9y4AlXka7t0C&pg=PA28 |year=2011 |volume=74 |publisher=Academic Press |isbn=978-0-12-385897-9 |pages=27–28 |doi=10.1016/B978-0-12-385897-9.00001-X |pmid=21295676 }}</ref><ref name=PoulinRandhawa2015>{{cite journal |last1=Poulin |first1=Robert |author1-link=Robert Poulin (zoologist) |last2=Randhawa |first2=Haseeb S. |title=Evolution of parasitism along convergent lines: from ecology to genomics |journal=Parasitology |date=February 2015 |volume=142 |issue=Suppl 1 |pages=S6–S15 |doi=10.1017/S0031182013001674 |pmc=4413784 |pmid=24229807}} {{open access}}</ref> for example, many ]n bugs have piercing and sucking mouthparts, adapted for feeding on plant sap,<ref name=Gullan>{{cite book |author1=Gullan, P.J. |author2=Cranston, P.S. |title=The Insects: An Outline of Entomology, 5th Edition |url=https://books.google.com/books?id=lF5hBAAAQBAJ&pg=PT790 |year=2014 |publisher=Wiley |isbn=978-1-118-84616-2 |pages=80–81, 790–}}</ref><ref>{{cite journal |last1=Labandeira |first1=Conrad C. |title=Early History of Arthropod and Vascular Plant Associations |journal=Annual Review of Earth and Planetary Sciences |date=May 1998 |volume=26 |pages=329–377 |doi=10.1146/annurev.earth.26.1.329 |bibcode=1998AREPS..26..329L }}</ref> while species in groups such as ]s, ], and ]es are ], feeding on the ] of animals.<ref name=PoulinRandhawa2015/> | |||
<gallery class=center mode=nolines widths=180 heights=180> | |||
File:CSIRO ScienceImage 2357 Spotted alfalfa aphid being attacked by parasitic wasp.jpg|A ] ovipositing into an ]<ref name="WilsonSwincer1982">{{cite journal |last1=Wilson |first1=C. G. |last2=Swincer |first2=D. E. |last3=Walden |first3=K. J. |title=The Introduction of Trioxys Complanatus Quilis (Hymenoptera: Aphidiidae), an Internal Parasite of the Spotted Alfalfa Aphid, into South Australia |journal=Australian Journal of Entomology |volume=21 |issue=1 |year=1982 |pages=13–27 |doi=10.1111/j.1440-6055.1982.tb01758.x|s2cid=84996305 }}</ref> | |||
File:Wilting a twig (4608641762).jpg|Plant parasite or ]: a ] bug sucking plant sap | |||
File:Male human head louse.jpg|] are directly transmitted ] ectoparasites. | |||
</gallery> | |||
== Relationship to humans == | == Relationship to humans == | ||
{{main|Human interactions with insects}} | |||
=== As pests === | === As pests === | ||
{{See also|Pest insect}} | |||
]'', a parasite, is the vector of ] and ]]] | |||
Many insects are considered ] by humans. Insects commonly regarded as pests include those that are parasitic (''e.g.'' ], ]), ] (]es, ]), damage structures (]s), or destroy agricultural goods (]s, ]s). Many ]s are involved in various forms of pest control, as in research for companies to produce ]s, but increasingly rely on methods of ], or biocontrol. Biocontrol uses one organism to reduce the population density of another organism—the pest—and is considered a key element of ].<ref>{{cite journal | title=Biological control and sustainable food production | last1=Bale | first1=JS | last2=van Lenteren | first2=JC | last3=Bigler | journal=Philosophical Transactions of the Royal Society of London. Series B, Biological Sciences | date=27 February 2008| volume=363 | issue=1492 | pages=761–776 | doi=10.1098/rstb.2007.2182 | pmid=17827110 | pmc=2610108 | first3=F.}}</ref><ref>{{cite book|author=Davidson, E. | year=2006 | title=Big Fleas Have Little Fleas: How Discoveries of Invertebrate Diseases Are Advancing Modern Science| isbn= 978-0-8165-2544-7|publisher=University of Arizona Press|location=Tucson, Ariz.}}</ref> | |||
]'', the ] mosquito, is a ] of several ].]] | |||
Despite the large amount of effort focused at controlling insects, human attempts to kill pests with insecticides can backfire. If used carelessly, the poison can kill all kinds of organisms in the area, including insects' natural predators, such as birds, mice and other insectivores. The effects of ]'s use exemplifies how some insecticides can threaten wildlife beyond intended populations of pest insects.<ref>{{cite journal | title=Developmental effects of endocrine-disrupting chemicals in wildlife and humans | last1=Colborn | first1=T | last2=vom Saal | first2=FS | last3=Soto | first3=AM | journal=Environmental Health Perspectives |date=October 1993 | volume=101 | issue=5 | pages=378–384 | pmc=1519860 | pmid=8080506 | doi=10.2307/3431890 | jstor=3431890}}</ref><ref>{{cite journal | title=Extinction risk to bird populations caused by DDT exposure | last1=Nakamaru | first1=M | last2=Iwasab | first2=Y | last3=Nakanishic | first3=J | journal=Chemosphere |date=October 2003 | volume=53 | issue=4 | pages=377–387 | doi=10.1016/S0045-6535(03)00010-9 | pmid=12946395| bibcode=2003Chmsp..53..377N }}</ref> | |||
{{main|Pest insect}} | |||
Many insects are considered ] by humans. These include parasites of people and livestock, such as ] and ]; ]es act as ] of ]. Other pests include insects like ]s that damage wooden structures; herbivorous insects such as ]s, aphids, and ] that destroy agricultural crops, or like ]s damage stored agricultural produce. Farmers have often attempted to control insects with chemical ]s, but increasingly rely on ]. This uses one organism to reduce the population density of a pest organism; it is a key element of ].<ref>{{cite journal |title=Biological control and sustainable food production |last1=Bale |first1=J. S. |last2=van Lenteren |first2=J. C. |last3=Bigler |first3=F. |journal=Philosophical Transactions of the Royal Society of London. Series B, Biological Sciences |date=27 February 2008|volume=363 |issue=1492 |pages=761–776 |doi=10.1098/rstb.2007.2182 |pmid=17827110 |pmc=2610108}}</ref><ref>{{cite book |last=Davidson |first=E. |title=Big Fleas Have Little Fleas: How Discoveries of Invertebrate Diseases Are Advancing Modern Science |year=2006 |publisher=University of Arizona Press |location=Tucson, Arizona |url=https://archive.org/details/bigfleashavelitt0000davi |url-access=registration |isbn=978-0-8165-2544-7 }}</ref> Biological control is favored because insecticides can cause harm to ecosystems far beyond the intended pest targets.<ref>{{cite journal |last1=Colborn |first1=T. |last2=vom Saal |first2=F. S. |last3=Soto |first3=A. M. |title=Developmental effects of endocrine-disrupting chemicals in wildlife and humans |journal=Environmental Health Perspectives |date=October 1993 |volume=101 |issue=5 |pages=378–384 |pmc=1519860 |pmid=8080506 |doi=10.2307/3431890 |jstor=3431890}}</ref><ref>{{cite journal |title=Extinction risk to bird populations caused by DDT exposure |last1=Nakamaru |first1=M. |last2=Iwasab |first2=Y. |last3=Nakanishic |first3=J. |journal=Chemosphere |date=October 2003 |volume=53 |issue=4 |pages=377–387 |doi=10.1016/S0045-6535(03)00010-9 |pmid=12946395 |bibcode=2003Chmsp..53..377N }}</ref> | |||
=== In beneficial roles === | === In beneficial roles === | ||
{{See also|Economic entomology#Beneficial insects}} | {{See also|Economic entomology#Beneficial insects}} | ||
], some insects are critical to agriculture. This ] is gathering nectar while pollen collects on its body.]] | |||
] with its prey, a ]. ] relationships such as these help control insect populations.]] | |||
]s were ] for ] over 5,000 years ago.<ref>{{cite journal |last1=Yu |first1=Hong-Song |last2=Shen |first2=Yi-Hong |last3=Yuan |first3=Gang-Xiang |display-authors=et al |title=Evidence of selection at melanin synthesis pathway loci during silkworm domestication |journal=Molecular Biology and Evolution |volume=28 |issue=6 |pages=1785–99 |year=2011 |pmid =21212153 |doi=10.1093/molbev/msr002 |doi-access= }}</ref><ref>{{cite journal |last=Normile |first=Dennis |title=Sequencing 40 Silkworm Genomes Unravels History of Cultivation |journal=Science |volume=325 |issue=5944 |pages=1058–1059 |year=2009 |pmid=19713499 |doi=10.1126/science.325_1058a |bibcode = 2009Sci...325.1058N |doi-access=free }}</ref> Here, silk cocoons are being unrolled. ]] | |||
Although pest insects attract the most attention, many insects are beneficial to the ] and to ]s. Some insects, like ]s, ]s, ] and ]s, ] ]s. Pollination is a ] relationship between plants and insects. As insects gather ] from different plants of the same species, they also spread ] from plants on which they have previously fed. This greatly increases plants' ability to ], which maintains and possibly even improves their evolutionary ]. This ultimately affects humans since ensuring healthy crops is critical to ]. As well as pollination ants help with seed distribution of plants. This helps to spread the plants, which increases plant diversity. This leads to an overall better environment.<ref>{{cite book|last=Holldobler|first=Wilson|title=Journey to the ants: a story of scientific exploration|year=1994|publisher=Cambridge, Mass.:Belknap Press of Haravard University Press, 1994|location=Westminster college McGill Library|isbn=978-0-674-48525-9|pages=196–199}}</ref> A serious environmental problem is the ] insects, and a number of species of insects are now cultured primarily for ] in order to have sufficient pollinators in the field, ] or ] at ] time.<ref name="The 1991 Yearbook of Agriculture">{{cite book|last=Smith|first=Deborah T|title=Agriculture and the Environment: The 1991 Yearbook of Agriculture|publisher=United States Government Printing|date=1991|edition= 1991|isbn=978-0-16-034144-1|url=https://books.google.com/?id=fDTbAAAAMAAJ}}</ref>{{Rp|240–243}} Another solution, as shown in Delaware, has been to raise native plants to help support native pollinators like '']''.<ref name="Farming for native bees">Kuehn, F. Coordinator. (2015). . World Wide Web electronic publication. (Retrieved: September 22, 2015).</ref> Insects also produce useful substances such as ], ], ] and ]. ]s have been cultured by humans for thousands of years for honey, although contracting for crop pollination is becoming more significant for ]s. The ] has greatly affected human history, as ] established relationships between China and the rest of the world. | |||
] of flowering plants by insects including ]s, ], ], and ]s, is economically important.<ref>{{cite book |last=Holldobler |first=Wilson |title=Journey to the ants: a story of scientific exploration |year=1994 |location=Cambridge, Massachusetts |publisher=Belknap Press |isbn=978-0-674-48525-9 |pages= |url=https://archive.org/details/journeytoantss00holl/page/196}}</ref> The value of insect pollination of crops and fruit trees was estimated in 2021 to be about $34 billion in the US alone.<ref>{{Cite journal|last1=Jordan |first1=Alex |last2=Patch |first2=Harland M. |last3=Grozinger |first3=Christina M. |last4=Khanna |first4=Vikas |date=2021-01-26 |title=Economic Dependence and Vulnerability of United States Agricultural Sector on Insect-Mediated Pollination Service |url=https://pubs.acs.org/doi/pdf/10.1021/acs.est.0c04786 |journal=Environmental Science & Technology |volume=55 |issue=4 |pages=2243–2253 |doi=10.1021/acs.est.0c04786 |pmid=33496588 |bibcode=2021EnST...55.2243J |s2cid=231710967 }}</ref> | |||
] insects, or insects that feed on other insects, are beneficial to humans if they eat insects that could cause damage to agriculture and human structures. For example, ]s feed on crops and cause problems for farmers, but ]s feed on aphids, and can be used as a means to significantly reduce pest aphid populations. While ]s are perhaps more visible predators of insects, insects themselves account for the vast majority of insect consumption. Ants also help control animal populations by consuming small vertebrates.<ref>{{cite journal|last=Camargo|first=Rafael|author2=Paulo Oliveira|title=Natural history of the Neotrobical arboreal ant, ''Odontomachus hastatus'': Nest sites, foraging schedule, and diet|journal=Journal of Insect Science|date=2011|volume=12|issue=18|pages=48|pmid=22957686|pmc=3476954|doi=10.1673/031.012.4801}}</ref> Without predators to keep them in check, insects can undergo almost unstoppable ]s.<ref name="Gullan and Cranston" />{{Rp|328–348}}<ref name="Gullan and Cranston" />{{Rp|400}}<ref>{{cite web | title=Biocontrol Network – Beneficial Insects | url=http://www.biconet.com/biocontrol.html | publisher=Biocontrol Network | accessdate=9 May 2009}}</ref><ref>{{cite book |author1=Davidson, RH |author2=William F. Lyon | year=1979 | title=Insect Pests of Farm, Garden, and Orchard |publisher=Wiley, John & Sons |page= 38| isbn=978-0-471-86314-4}}</ref> | |||
Insects produce useful substances such as ],<ref name="Crane1990">{{cite journal |last=Crane |first=E. |title = Honey from honeybees and other insects |journal=Ethology Ecology & Evolution |volume=3 |issue=sup1 |pages=100–105 |year=1990 |doi=10.1080/03949370.1991.10721919 |author-link=Eva Crane }}</ref> ],<ref name=Sanford>{{cite journal |last1=Sanford |first1=M.T. |last2=Dietz |first2=A. |year=1976 |title=The fine structure of the wax gland of the honey bee (Apis mellifera L.). |journal=Apidologie |volume=7 |issue=3 |pages=197–207 |doi=10.1051/apido:19760301|doi-access=free }}</ref><ref>{{Cite news |url=https://www.beeculture.com/wax-rendering/ |title=Wax Rendering |date=23 March 2016 |work=Bee Culture |access-date=26 October 2018 }}</ref> ]<ref>{{cite news |title=How Shellac Is Manufactured |url=http://nla.gov.au/nla.news-article55073762 |access-date=17 July 2015 |publisher=The Mail (Adelaide, SA : 1912 – 1954) |date=18 Dec 1937}}</ref> and ].<ref>{{cite web |last=Bezzina |first=Neville |title=Silk Production Process |url=http://www.senature.com/sensemagazine/research-technologies/silk-production-process-go-behind-the-scenes-1701.html |publisher=Sense of Nature Research |url-status=dead |archive-url=https://web.archive.org/web/20120629231032/http://www.senature.com/sensemagazine/research-technologies/silk-production-process-go-behind-the-scenes-1701.html |archive-date=29 June 2012 }}</ref> ]s have been cultured by humans for thousands of years for honey.<ref>{{cite journal |last1=Dams |first1=M. |last2=Dams |first2=L. |title=Spanish Rock Art Depicting Honey Gathering During the Mesolithic |journal=Nature |date=21 July 1977 |volume=268 |issue=5617 |pages=228–230 |doi=10.1038/268228a0 |bibcode=1977Natur.268..228D |s2cid=4177275}}</ref> Beekeeping in pottery vessels began about 9,000 years ago in North Africa.<ref name=9kya>{{cite journal |last=Roffet-Salque |first=Mélanie |display-authors=et al|title=Widespread exploitation of the honeybee by early Neolithic farmers |journal=Nature |date=14 June 2016 |volume=534 |issue=7607 |pages=226–227 |doi=10.1038/nature18451 |pmid=26560301 |doi-access=free|hdl=10379/13692 |hdl-access=free }}</ref> The ] has greatly affected human history, as ] established relationships between China and the rest of the world.<ref>{{cite book |title=Chinese Silk: A Cultural History |last=Vainker |first=Shelagh |year=2004 |publisher=] |isbn=0813534461 |page=20}}</ref><ref>{{cite journal |last=Christian |first=David |year=2000 |title=Silk Roads or Steppe Roads? The Silk Roads in World History |journal=]|volume=2 |issue=1 |page=1 |doi=10.1353/jwh.2000.0004 |s2cid=18008906}}</ref> | |||
Insects are also used in medicine, for example fly larvae (]s) were formerly used to ] to prevent or stop ], as they would only consume dead flesh. This treatment is finding modern usage in some hospitals. Recently insects have also gained attention as potential sources of drugs and other medicinal substances.<ref>{{cite journal|last=Dossey|first=Aaron T.|date= December 2010|title=Insects and their chemical weaponry: New potential for drug discovery |journal=Natural Product Reports|volume=27 |pages= 1737–1757|url=http://pubs.rsc.org/en/Content/ArticleLanding/2010/NP/C005319H|doi=10.1039/c005319h|issue=12|pmid=20957283}}</ref> Adult insects, such as crickets and insect larvae of various kinds, are also commonly used as fishing bait.<ref>{{cite journal|last=Sherman|first=Ronald A.|author2=Pechter, Edward A. |date= 1987|title=Maggot therapy: a review of the therapeutic applications of fly larvae in human medicine, especially for treating osteomyelitis|journal=Medical and Veterinary Entomology|volume=2 |issue=3|pages= 225–230|doi=10.1111/j.1365-2915.1988.tb00188.x}}</ref> | |||
Insects that feed on or parasitise other insects are beneficial to humans if they thereby reduce damage to agriculture and human structures. For example, ]s feed on crops, causing economic loss, but ]s feed on aphids, and can be used ]. Insects account for the vast majority of insect consumption.{{sfn|Gullan|Cranston|2005|p=328–348, 400}}<ref>{{cite web |title=Biocontrol Network – Beneficial Insects |url=http://www.biconet.com/biocontrol.html |publisher=Biocontrol Network |access-date=9 May 2009 |archive-url=https://web.archive.org/web/20090228043847/http://www.biconet.com/biocontrol.html |archive-date=28 February 2009 |url-status=usurped }}</ref><ref>{{cite book |last1=Davidson |first1=R. H. |last2=Lyon |first2=William F. |year=1979 |title=Insect Pests of Farm, Garden, and Orchard |publisher=John Wiley & Sons |page=38 |isbn=978-0-471-86314-4}}</ref> | |||
Fly larvae (]s) were formerly ] to prevent or stop ], as they would only consume dead flesh. This treatment is finding modern usage in some hospitals. Insects have gained attention as potential sources of drugs and other medicinal substances.<ref>{{cite journal |last=Dossey |first=Aaron T. |date= December 2010 |title=Insects and their chemical weaponry: New potential for drug discovery |journal=Natural Product Reports |volume=27 |pages=1737–1757 |doi=10.1039/c005319h |issue=12 |pmid=20957283 }}</ref> Adult insects, such as crickets and insect larvae of various kinds, are commonly used as fishing bait.<ref>{{cite journal |last=Sherman |first=Ronald A. |author2=Pechter, Edward A. |date=1987 |title=Maggot therapy: a review of the therapeutic applications of fly larvae in human medicine, especially for treating osteomyelitis |journal=Medical and Veterinary Entomology |volume=2 |issue=3 |pages=225–230 |doi=10.1111/j.1365-2915.1988.tb00188.x |pmid=2980178 |s2cid=44543735}}</ref> | |||
=== Population declines === | |||
{{main|Decline in insect populations}} | |||
At least 66 insect species extinctions have been recorded since 1500, many of them on oceanic islands.<ref name="Briggs2017">{{cite journal |last1=Briggs |first1=John C |title=Emergence of a sixth mass extinction? |journal=Biological Journal of the Linnean Society |date=October 2017 |volume=122 |issue=2 |pages=243–248 |doi=10.1093/biolinnean/blx063|doi-access=free }}</ref> ] have been attributed to human activity in the form of artificial lighting,<ref name="Owens2018">{{cite journal |last1=Owens |first1=Avalon C. S. |last2=Lewis |first2=Sara M. |title=The impact of artificial light at night on nocturnal insects: A review and synthesis |journal=Ecology and Evolution |date=November 2018 |volume=8 |issue=22 |pages=11337–11358 |doi=10.1002/ece3.4557|pmid=30519447 |pmc=6262936 |bibcode=2018EcoEv...811337O }}</ref> land use changes such as urbanization or farming,<ref name="Tscharntke2005">{{cite journal |last1=Tscharntke |first1=Teja |last2=Klein |first2=Alexandra M. |last3=Kruess |first3=Andreas |last4=Steffan-Dewenter |first4=Ingolf |last5=Thies |first5=Carsten |title=Landscape perspectives on agricultural intensification and biodiversity and ecosystem service management |journal=Ecology Letters |date=August 2005 |volume=8 |issue=8 |pages=857–874 |doi=10.1111/j.1461-0248.2005.00782.x|bibcode=2005EcolL...8..857T |s2cid=54532666 |doi-access=free }}</ref><ref>{{cite book |title=Insect-plant interactions in a crop protection perspective |isbn=978-0-12-803324-1 |pages=313–320|date=2017-01-19 |publisher=Academic Press }}</ref> pesticide use,<ref>{{cite journal |last1=Braak |first1=Nora |last2=Neve |first2=Rebecca |last3=Jones |first3=Andrew K. |last4=Gibbs |first4=Melanie |last5=Breuker |first5=Casper J. |title=The effects of insecticides on butterflies – A review |journal=Environmental Pollution |date=November 2018 |volume=242 |issue=Pt A |pages=507–518 |doi=10.1016/j.envpol.2018.06.100|pmid=30005263 |bibcode=2018EPoll.242..507B |s2cid=51625489 |url=https://radar.brookes.ac.uk/radar/items/fddc88d3-25f2-4274-9321-2f9b3b72047a/1 }}</ref> and invasive species.<ref>{{cite journal |last1=Wagner |first1=David L. |last2=Van Driesche |first2=Roy G. |title=Threats Posed to Rare or Endangered Insects by Invasions of Nonnative Species |journal=Annual Review of Entomology |date=January 2010 |volume=55 |issue=1 |pages=547–568 |doi=10.1146/annurev-ento-112408-085516|pmid=19743915 }}</ref><ref>{{cite web |url=http://www.globalchange.umich.edu/globalchange2/current/lectures/biodiversity/biodiversity.html |archive-url=https://web.archive.org/web/20150220154543/http://www.globalchange.umich.edu/globalchange2/current/lectures/biodiversity/biodiversity.html |archive-date=20 February 2015 |title=Threats to Global Diversity |last=Wilson |first=E. O. |access-date=17 May 2009}}</ref> A 2019 research review suggested that a large proportion of insect species is<!--singular: "a proportion is"--> threatened with extinction in the 21st century,<ref name="Wyckhuys2019">{{cite journal |last1=Sánchez-Bayo |first1=Francisco |last2=Wyckhuys |first2=Kris A.G. |title=Worldwide decline of the entomofauna: A review of its drivers |journal=Biological Conservation |date=April 2019 |volume=232 |pages=8–27 |doi=10.1016/j.biocon.2019.01.020 |doi-access=free |bibcode=2019BCons.232....8S }}</ref> though the details have been disputed.<ref>{{cite web |last1=Saunders |first1=Manu |title=Insectageddon is a great story. But what are the facts? |url=https://ecologyisnotadirtyword.com/2019/02/16/insectageddon-is-a-great-story-but-what-are-the-facts/ |website=Ecology is not a dirty word |access-date=24 February 2019 |date=16 February 2019 |archive-url=https://web.archive.org/web/20190225044750/https://ecologyisnotadirtyword.com/2019/02/16/insectageddon-is-a-great-story-but-what-are-the-facts/ |archive-date=25 February 2019 |url-status=live }}</ref> A larger 2020 meta-study, analyzing data from 166 long-term surveys, suggested that populations of terrestrial insects are indeed decreasing rapidly, by about 9% per decade.<ref name=vanKlink2020>{{citation |journal=] |title=Meta-analysis reveals declines in terrestrial but increases in freshwater insect abundances|first1=Roel |last1=van Klink |date=24 April 2020|volume=368 |issue=6489 |pages=417–420 |doi=10.1126/science.aax9931 |pmid=32327596 |bibcode=2020Sci...368..417V |s2cid=216106896 |doi-access=free }}</ref><ref>{{Cite news |last=McGrath |first=Matt |url=https://www.bbc.com/news/science-environment-52399373 |title='Insect apocalypse' more complex than thought |date=23 April 2020 |work=BBC News |access-date=2020-04-24 }}</ref> | |||
=== In research === | === In research === | ||
]'' is one of the most widely used organisms in biological research.]] | |||
]'' is a widely used ].]] | |||
Insects play important roles in biological research. For example, because of its small size, short generation time and high ], the common fruit fly '']'' is a ] for studies in the ] of higher ]s. ''D. melanogaster'' has been an essential part of studies into principles like ], ], ] genetics, ], behavior and ]. Because genetic systems are well conserved among eukaryotes, understanding basic cellular processes like ] or ] in fruit flies can help to understand those processes in other eukaryotes, including humans.<ref name="Pierce">{{cite book | title=Genetics: A Conceptual Approach | author=Pierce, BA | edition= 2nd | publisher=W.H. Freeman and Company | location=New York | page=87 | isbn=978-0-7167-8881-2 | year=2006}}</ref> The ] of ''D. melanogaster'' was ] in 2000, reflecting the organism's important role in biological research. It was found that 70% of the fly genome is similar to the human genome, supporting the evolution theory.<ref name="Adams_2000">{{cite journal | last1=Adams | first=MD | title=The genome sequence of ''Drosophila melanogaster'' | journal=Science | volume=287 | issue=5461 | pages=2185–2195 | date=24 March 2000| pmid=10731132 | doi=10.1126/science.287.5461.2185 | last2=Celniker | first2=SE | last3=Holt | first3=RA | last4=Evans | first4=CA | last5=Gocayne | first5=JD | last6=Amanatides | first6=PG | last7=Scherer | first7=SE | last8=Li | first8=PW | last9=Hoskins | first9=RA | last10=Galle | first10=R.F. | last11=George | first11=R.A. | last12=Lewis | first12=S.E. | last13=Richards | first13=S | last14=Ashburner | first14=M | last15=Henderson | first15=S.N. | last16=Sutton | first16=G.G. | last17=Wortman | first17=J.R. | last18=Yandell | first18=M.D. | last19=Zhang | first19=Q | last20=Chen | first20=L.X. | last21=Brandon | first21=R.C. | last22=Rogers | first22=Y.H. | last23=Blazej | first23=R.G. | last24=Champe | first24=M | last25=Pfeiffer | first25=B.D. | last26=Wan | first26=K.H. | last27=Doyle | first27=C | last28=Baxter | first28=E.G. | last29=Helt | first29=G | last30=Nelson | first30=C.R. | bibcode=2000Sci...287.2185.| display-authors=8| citeseerx=10.1.1.549.8639 }}</ref> | |||
Insects play important roles in biological research. For example, because of its small size, short generation time and high ], the common fruit fly '']'' is a ] for studies in the ] of ]s, including ], ], ] genetics, ], behavior and ]. Because genetic systems are well conserved among eukaryotes, understanding basic cellular processes like ] or ] in fruit flies can help to understand those processes in other eukaryotes, including humans.<ref name="Pierce">{{cite book |title=Genetics: A Conceptual Approach |last=Pierce |first=B. A. |edition=2nd |publisher=W.H. Freeman and Company |location=New York |page= |isbn=978-0-7167-8881-2 |year=2006 |url=https://archive.org/details/geneticsconceptu0000unse/page/87 }}</ref> The ] of ''D. melanogaster'' was ] in 2000, reflecting the organism's important role in biological research. It was found that 70% of the fly genome is similar to the ], supporting the theory of ].<ref name="Adams_2000">{{cite journal |last1=Adams |first1=M. D. |title=The genome sequence of ''Drosophila melanogaster'' |journal=Science |volume=287 |issue=5461 |pages=2185–2195 |date=24 March 2000 |pmid=10731132 |doi=10.1126/science.287.5461.2185 |last2=Celniker |first2=S. E. |last3=Holt |first3=R. A. |last4=Evans |first4=C. A. |last5=Gocayne |first5=J. D. |last6=Amanatides |first6=P. G. |last7=Scherer |first7=S. E. |last8=Li |first8=P. W. |last9=Hoskins |first9=R. A. |last10=Galle |first10=R. F. |last11=George |first11=R. A. |last12=Lewis |first12=S.E. |last13=Richards |first13=S. |last14=Ashburner |first14=M. |last15=Henderson |first15=S. N. |last16=Sutton |first16=G. G. |last17=Wortman |first17=J. R. |last18=Yandell |first18=M. D. |last19=Zhang |first19=Q. |last20=Chen |first20=L.X. |last21=Brandon |first21=R. C. |last22=Rogers |first22=Y. H. |last23=Blazej |first23=R. G. |last24=Champe |first24=M. |last25=Pfeiffer |first25=B. D. |last26=Wan |first26=K. H. |last27=Doyle |first27=C. |last28=Baxter |first28=E. G. |last29=Helt |first29=G. |last30=Nelson |first30=C. R. |bibcode=2000Sci...287.2185. |display-authors=5 |citeseerx=10.1.1.549.8639 }}</ref> | |||
=== As food === | === As food === | ||
{{Main|Entomophagy}} | |||
In some cultures, insects, especially ] ]s, are considered to be ], whereas in other places they form part of the normal diet. Insects have a high protein content for their mass, and some authors suggest their potential as a major source of ] in human ].<ref name="Gullan and Cranston" />{{Rp|10–13}} In most first-world countries, however, ] (the eating of insects), is ].<ref>{{cite book|last=Michels|first=John|others=American Association for the Advance of Science|title=Science|editor=John Michels|publisher=American Association for the Advance of Science|location=229 Broadway ave., N.Y.|year=1880|volume=1|pages=2090pp|url=https://books.google.com/?id=aDkLAAAAYAAJ&pg=PA69|isbn=978-1-930775-36-7}}</ref> | |||
Since it is impossible to entirely eliminate pest insects from the human food chain, insects are inadvertently present in many foods, especially grains. ] laws in many countries do not prohibit insect parts in food, but rather limit their quantity. According to ] anthropologist ], the eating of insects is taboo in cultures that have other protein sources such as fish or livestock. | |||
{{main|Insects as food}} | |||
Due to the abundance of insects and a worldwide concern of food shortages, the ] of the ] considers that the world may have to, in the future, regard the prospects of eating insects as a food staple. Insects are noted for their nutrients, having a high content of protein, minerals and fats and are eaten by one-third of the global population.<ref name="investvine">{{cite web|url=http://investvine.com/un-bugs-are-food-of-the-future-video/|title=UN: Insects are 'food of the future' (video)|first=Arno|last=Maierbrugger|work=Inside Investor|date=14 May 2013|accessdate=17 May 2013}}</ref> | |||
]s are prized as high-protein foods by Aboriginal Australians.<ref name="Ceurstemont 2013">{{cite journal |last1=Ceurstemont |first1=Sandrine |title=Inevitable insectivores? Not so fast |date=6 July 2013 |url=https://www.sciencedirect.com/science/article/abs/pii/S0262407913616917 |journal=New Scientist |volume=219 |issue=2924 |pages=35 |doi=10.1016/S0262-4079(13)61691-7 |access-date=3 December 2021 }}</ref>]] | |||
=== In culture === | |||
{{Main|Insects in culture}} | |||
Insects are consumed as food in 80% of the world's nations, by people in roughly 3,000 ethnic groups.<ref name="theguardian">{{Cite news |date=2010-07-31 |title=Insects could be the key to meeting food needs of growing global population|url=http://www.theguardian.com/environment/2010/aug/01/insects-food-emissions |access-date=2022-01-13 |work=] }}</ref><ref name="Ramos-Elorduy 1998 44">{{cite book |title=Creepy crawly cuisine: the gourmet guide to edible insects |last=Ramos-Elorduy |first=Julieta |author2=Menzel, Peter |year=1998 |publisher=Inner Traditions / Bear & Company |isbn=978-0-89281-747-4 |page=44 |url=https://books.google.com/books?id=Q7f1LkFz11gC |access-date=23 April 2014}}</ref> In Africa, locally abundant species of ]s and ]s are a common traditional human food source.<ref name="buginfo_asfood">{{cite web |title=Insects as Food for Humans |url=https://www.si.edu/spotlight/buginfo/insects-food |access-date = 14 September 2022 }}</ref> Some, especially ] ]s, are considered to be ]. Insects have a high protein content for their mass, and some authors suggest their potential as a major source of ] in human ].{{sfn|Gullan|Cranston|2005|pp=10–13}} In most first-world countries, however, ] (the eating of insects), is ].<ref>{{cite book |last=Michels |first=John |title=Science |editor=John Michels |publisher=American Association for the Advance of Science |location=New York |year=1880 |volume=1 |page=69 |url=https://books.google.com/books?id=aDkLAAAAYAAJ&pg=PA69 <!--|isbn=978-1-930775-36-7-->}}</ref> They are also recommended by ] as a ] food for troops in adversity.<ref name="buginfo_asfood"/> Because of the abundance of insects and a worldwide concern of food shortages, the ] of the ] considers that people throughout the world may have to eat insects as a food staple. Insects are noted for their nutrients, having a high content of protein, minerals and fats and are already regularly eaten by one-third of the world's population.<ref name="investvine">{{cite web |url=http://investvine.com/un-bugs-are-food-of-the-future-video/ |title=UN: Insects are 'food of the future' (video) |first=Arno |last=Maierbrugger |work=Inside Investor |date=14 May 2013 |access-date=17 May 2013 |archive-url=https://web.archive.org/web/20130910061538/http://investvine.com/un-bugs-are-food-of-the-future-video/ |archive-date=10 September 2013 |url-status=live}}</ref> | |||
] held religious and cultural symbolism in ], ] and some shamanistic Old World cultures. The ancient ] regarded ]s as symbols of rebirth or immortality. In ]n literature, the epic poem of ] has allusions to ] that signify the impossibility of immortality. Among the ] of ] of the ] language groups, honey ants and witchety grubs served as personal clan totems. In the case of the 'San' bush-men of the ], it is the ] that holds much cultural significance including creation and zen-like patience in waiting.<ref name="Gullan and Cranston" />{{Rp|9}} | |||
=== In other products === | |||
] larvae can provide ] and fats for use in ].<ref>{{cite journal |last1=Verheyen |first1=Geert |last2=Ooms|first2=Tom |last3=Vogels|first3=Liesbeth |last4=Vreysen |first4=Steven |last5=Bovy |first5=Ann |last6=Van Miert |first6=Sabine |last7=Meersman |first7=Filip |date=2018-05-01 |title=Insects as an Alternative Source for the Production of Fats for Cosmetics |url=https://www.researchgate.net/publication/326671736 |journal=Journal of Cosmetic Science |volume=69 |issue=3 |pages=187–202 |pmid=30052193}}</ref> Insect cooking oil, insect butter and ]s ] such insects as the superworm ('']'').<ref>{{Cite web |date=2016-08-15 |title=From Pest to Pot: Can Insects Feed the World? |url=https://www.nationalgeographic.com/culture/article/sponsor-content-from-pest-pot-can-insects-feed-the-world |archive-url=https://web.archive.org/web/20210410150413/https://www.nationalgeographic.com/culture/article/sponsor-content-from-pest-pot-can-insects-feed-the-world |url-status=dead |archive-date=10 April 2021 |access-date=2022-01-13 |website=National Geographic Culture}}</ref> Insect species including the black soldier fly or the ] in their ] forms, and beetle larvae such as ], can be processed and ] for farmed animals including chicken, fish and pigs.<ref>{{Cite magazine |title=How AgriProtein makes chicken food from maggots |magazine=Wired UK |url=https://www.wired.co.uk/article/food-of-larvae |access-date=2022-01-13 }}</ref> Many species of insects are sold and kept as ]s.<ref>{{Cite web |last=Bugs |title=Bugs – das Wirbellosenmagazin |url=https://www.ms-verlag.de/magazine/bugs |access-date=7 March 2021|website=NTV Verlag}}</ref> | |||
=== In religion and folklore === | |||
{{further|Insects in mythology}} | |||
]ian ] with separate wings, c. 712-342 BC]] | |||
] held religious and cultural symbolism in ], ] and some ] Old World cultures. The ancient ] regarded ]s as symbols of rebirth or immortality. In ]n literature, the epic poem of ] has allusions to ] that signify the impossibility of immortality. Among the ] of ] of the ] language groups, honey ants and ]s served as personal clan totems. In the case of the ] of the ], it is the ] that holds much cultural significance including creation and ]-like patience in waiting.{{sfn|Gullan|Cranston|2005|p=9}} | |||
==See also== | ==See also== | ||
{{Misplaced Pages books|1=Introduction to Insects|3=Insect}} | |||
{{Portal|Insects|Arthropods|Animals|Biology}} | |||
* ] | |||
* ] | |||
* ] | * ] | ||
* ] | * ] | ||
* ] | * ] | ||
* ] | |||
* ] | |||
* ] | * ] | ||
* ] | |||
* ] | |||
== |
== Notes == | ||
{{Reflist|32em|refs= | |||
<ref name=HughLong16>{{Cite book |last1=Hughes |first1=Joseph |last2=Longhorn |first2=Stuart |date=2016 |editor1-last=Olson |editor1-first=Peter D. |editor2-last=Hughes |editor2-first=Joseph |editor3-last=Cotton |editor3-first=James A. |contribution=The role of next generation sequencing technologies in shaping the future of insect molecular systematics |title=Next Generation Systematics |pages=28–61 |publisher=Cambridge University Press |isbn=978-1-139-23635-5 |contribution-url=https://books.google.com/books?hl=en&lr=&id=C3JNDAAAQBAJ&oi=fnd&pg=PA28 |accessdate=2017-07-27 |lastauthoramp=yes }}, pp. 29–30</ref> | |||
{{notelist}} | |||
<ref name=Kjer>{{Cite journal |last1=Kjer |first1=Karl M. |last2=Simon |first2=Chris |last3=Yavorskaya |first3=Margarita |last4=Beutel |first4=Rolf G. |date=2016 |title=Progress, pitfalls and parallel universes: a history of insect phylogenetics |journal=Journal of the Royal Society Interface |volume=13 |issue=121 |page=121 |doi=10.1098/rsif.2016.0363 |pmid=27558853 |lastauthoramp=yes |pmc=5014063 }}</ref> | |||
== References == | |||
<ref name=Sasaki>{{Cite journal |last1=Sasaki |first1=Go |last2=Sasaki |first2=Keisuke |last3=Machida |first3=Ryuichiro |last4=Miyata |first4=Takashi |last5=Su |first5=Zhi-Hui |date=2013 |title=Molecular phylogenetic analyses support the monophyly of Hexapoda and suggest the paraphyly of Entognatha |journal=BMC Evolutionary Biology |volume=13 |page=236 |doi=10.1186/1471-2148-13-236 |pmid=24176097 |pmc=4228403 |lastauthoramp=yes }}</ref> | |||
}} | |||
{{Reflist|30em}} | |||
== Sources == | |||
* {{cite book |last1=Gullan |first1=P. J. |last2=Cranston |first2=P. S. |title=The Insects: An Outline of Entomology |publisher=Blackwell Publishing |location=Oxford |year=2005 |edition=3rd |isbn=978-1-4051-1113-3 |url=https://archive.org/details/isbn_9781405111133 }} | |||
* {{cite book |last1=Gullan |first1=P. J. |last2=Cranston |first2=P. S. |title=The Insects: An Outline of Entomology |publisher=Wiley Blackwell |location=Oxford |year=2014 |edition=5th |isbn=978-1-118-84616-2 |url=https://books.google.com/books?id=lF5hBAAAQBAJ }} | |||
* {{cite book |last=Nation |first=James L. |title=Insect Physiology and Biochemistry |publisher=CRC Press |year=2001 |edition=1st |isbn=978-0-8493-1181-9 |url=https://books.google.com/books?id=l3v2tOvz1uQC}} | |||
* {{cite book |last1=Resh |first1=Vincent H. |last2=Carde |first2=Ring T. |title=Encyclopedia of Insects |publisher=Academic Press |date=2009 |edition=2 |isbn=978-0-12-374144-8}} | |||
* {{cite book |last=Schowalter |first=Timothy Duane |title=Insect Ecology: An Ecosystem Epproach |edition=2nd (illustrated) |year=2006 |publisher=Academic Press |isbn=978-0-12-088772-9 |url=https://books.google.com/books?id=3PD6R-AEvwEC |access-date=27 October 2015 |archive-url=https://web.archive.org/web/20160603221311/https://books.google.com/books?id=3PD6R-AEvwEC |archive-date=3 June 2016 |url-status=live}} | |||
== External links == | |||
==Bibliography== | |||
* {{Citation |last1=Chinery |first1=Michael |date=1993 |title=Insects of Britain & Northern Europe |edition= 3rd |location=London, etc. |publisher=HarperCollins |isbn=978-0-00-219918-6 }} | |||
{{Spoken Misplaced Pages|WP en Insect Intro 30 Oct 2010.ogg|date=2010-10-30}} | |||
==Further reading== | |||
* Vogel, Gretchen (May 2017). '']''. {{doi|10.1126/science.aal1160}}. | |||
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==External links== | |||
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* | * | ||
* {{EOL}} | * {{EOL}} | ||
* ] | * ] | ||
* – Insecta, | * – Insecta, | ||
* : Holotypes at the International Palaeoentological Society | |||
* Overview of insect external and internal anatomy | |||
* International Palaeoentological Society | |||
* | * | ||
* 24,000 high resolution insect photographs | * 24,000 high resolution insect photographs | ||
* Insect news, and video clips from BBC programmes past and present. | |||
* Many insect video clips. | |||
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Latest revision as of 01:44, 21 December 2024
Class of arthropods For other uses, see Insect (disambiguation).
Insect Temporal range: Carboniferous–Present PreꞒ Ꞓ O S D C P T J K Pg N | |
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Insects have a three-part body: head with large compound eyes and antennae, a thorax with three pairs of legs, and a segmented abdomen. Many groups also have two pairs of wings. | |
Scientific classification | |
Domain: | Eukaryota |
Kingdom: | Animalia |
Phylum: | Arthropoda |
Clade: | Pancrustacea |
Subphylum: | Hexapoda |
Class: | Insecta Linnaeus, 1758 |
Subgroups | |
Synonyms | |
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Insects (from Latin insectum) are hexapod invertebrates of the class Insecta. They are the largest group within the arthropod phylum. Insects have a chitinous exoskeleton, a three-part body (head, thorax and abdomen), three pairs of jointed legs, compound eyes, and a pair of antennae. Insects are the most diverse group of animals, with more than a million described species; they represent more than half of all animal species.
The insect nervous system consists of a brain and a ventral nerve cord. Most insects reproduce by laying eggs. Insects breathe air through a system of paired openings along their sides, connected to small tubes that take air directly to the tissues. The blood therefore does not carry oxygen; it is only partly contained in vessels, and some circulates in an open hemocoel. Insect vision is mainly through their compound eyes, with additional small ocelli. Many insects can hear, using tympanal organs, which may be on the legs or other parts of the body. Their sense of smell is via receptors, usually on the antennae and the mouthparts.
Nearly all insects hatch from eggs. Insect growth is constrained by the inelastic exoskeleton, so development involves a series of molts. The immature stages often differ from the adults in structure, habit and habitat. Groups that undergo four-stage metamorphosis often have a nearly immobile pupa. Insects that undergo three-stage metamorphosis lack a pupa, developing through a series of increasingly adult-like nymphal stages. The higher level relationship of the insects is unclear. Fossilized insects of enormous size have been found from the Paleozoic Era, including giant dragonfly-like insects with wingspans of 55 to 70 cm (22 to 28 in). The most diverse insect groups appear to have coevolved with flowering plants.
Adult insects typically move about by walking and flying; some can swim. Insects are the only invertebrates that can achieve sustained powered flight; insect flight evolved just once. Many insects are at least partly aquatic, and have larvae with gills; in some species, the adults too are aquatic. Some species, such as water striders, can walk on the surface of water. Insects are mostly solitary, but some, such as bees, ants and termites, are social and live in large, well-organized colonies. Others, such as earwigs, provide maternal care, guarding their eggs and young. Insects can communicate with each other in a variety of ways. Male moths can sense the pheromones of female moths over great distances. Other species communicate with sounds: crickets stridulate, or rub their wings together, to attract a mate and repel other males. Lampyrid beetles communicate with light.
Humans regard many insects as pests, especially those that damage crops, and attempt to control them using insecticides and other techniques. Others are parasitic, and may act as vectors of diseases. Insect pollinators are essential to the reproduction of many flowering plants and so to their ecosystems. Many insects are ecologically beneficial as predators of pest insects, while a few provide direct economic benefit. Two species in particular are economically important and were domesticated many centuries ago: silkworms for silk and honey bees for honey. Insects are consumed as food in 80% of the world's nations, by people in roughly 3,000 ethnic groups. Human activities are having serious effects on insect biodiversity.
Etymology
The word insect comes from the Latin word insectum from in, "cut up", as insects appear to be cut into three parts. The Latin word was introduced by Pliny the Elder who calqued the Ancient Greek word ἔντομον éntomon "insect" (as in entomology) from ἔντομος éntomos "cut in pieces"; this was Aristotle's term for this class of life in his biology, also in reference to their notched bodies. The English word insect first appears in 1601 in Philemon Holland's translation of Pliny.
Insects and other bugs
Distinguishing features
In common speech, insects and other terrestrial arthropods are often called bugs. Entomologists to some extent reserve the name "bugs" for a narrow category of "true bugs", insects of the order Hemiptera, such as cicadas and shield bugs. Other terrestrial arthropods, such as centipedes, millipedes, woodlice, spiders, mites and scorpions, are sometimes confused with insects, since they have a jointed exoskeleton. Adult insects are the only arthropods that ever have wings, with up to two pairs on the thorax. Whether winged or not, adult insects can be distinguished by their three-part body plan, with head, thorax, and abdomen; they have three pairs of legs on the thorax.
- Insects and other bugs that could be confused with them
-
Insect: Six legs, three-part body
(head, thorax, abdomen),
up to two pairs of wings -
Spider: eight legs,
two-part body - Woodlouse: seven pairs of legs, seven body segments (plus head and tail)
-
Centipede: many legs,
one pair per segment -
Millipede: many legs,
two pairs per segment
Diversity
Main article: Insect biodiversityEstimates of the total number of insect species vary considerably, suggesting that there are perhaps some 5.5 million insect species in existence, of which about one million have been described and named. These constitute around half of all eukaryote species, including animals, plants, and fungi. The most diverse insect orders are the Hemiptera (true bugs), Lepidoptera (butterflies and moths), Diptera (true flies), Hymenoptera (wasps, ants, and bees), and Coleoptera (beetles), each with more than 100,000 described species.
- Insects are extremely diverse. Five groups each have over 100,000 described species.
-
True bugs
(Hemiptera) -
Butterflies and moths
(Lepidoptera) -
Flies
(Diptera) -
Wasps
(Hymenoptera) -
Beetles
(Coleoptera)
Distribution and habitats
- Insects occur in habitats as varied as snow, freshwater, the tropics, desert, and even the sea.
- The snow scorpionfly Boreus hyemalis on snow
- The great diving beetle Dytiscus marginalis larva in a pond
- The green orchid bee Euglossa dilemma of Central America
- The desert locust Schistocerca gregaria laying eggs in sand
- Sea skater Halobates on a Hawaii beach
Insects are distributed over every continent and almost every terrestrial habitat. There are many more species in the tropics, especially in rainforests, than in temperate zones. The world's regions have received widely differing amounts of attention from entomologists. The British Isles have been thoroughly surveyed, so that Gullan and Cranston 2014 state that the total of around 22,500 species is probably within 5% of the actual number there; they comment that Canada's list of 30,000 described species is surely over half of the actual total. They add that the 3,000 species of the American Arctic must be broadly accurate. In contrast, a large majority of the insect species of the tropics and the southern hemisphere are probably undescribed. Some 30–40,000 species inhabit freshwater; very few insects, perhaps a hundred species, are marine. Insects such as snow scorpionflies flourish in cold habitats including the Arctic and at high altitude. Insects such as desert locusts, ants, beetles, and termites are adapted to some of the hottest and driest environments on earth, such as the Sonoran Desert.
Phylogeny and evolution
External phylogeny
Insects form a clade, a natural group with a common ancestor, among the arthropods. A phylogenetic analysis by Kjer et al. (2016) places the insects among the Hexapoda, six-legged animals with segmented bodies; their closest relatives are the Diplura (bristletails).
Hexapoda |
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Internal phylogeny
The internal phylogeny is based on the works of Wipfler et al. 2019 for the Polyneoptera, Johnson et al. 2018 for the Paraneoptera, and Kjer et al. 2016 for the Holometabola. The numbers of described extant species (boldface for groups with over 100,000 species) are from Stork 2018.
Insecta |
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Taxonomy
Early
Further information: Aristotle's biology § Classification, and Insecta in the 10th edition of Systema NaturaeDiagram of Linnaeus's key to his seven orders of insect, 1758
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Aristotle was the first to describe the insects as a distinct group. He placed them as the second-lowest level of animals on his scala naturae, above the spontaneously generating sponges and worms, but below the hard-shelled marine snails. His classification remained in use for many centuries.
In 1758, in his Systema Naturae, Carl Linnaeus divided the animal kingdom into six classes including Insecta. He created seven orders of insect according to the structure of their wings. These were the wingless Aptera, the two-winged Diptera, and five four-winged orders: the Coleoptera with fully-hardened forewings; the Hemiptera with partly-hardened forewings; the Lepidoptera with scaly wings; the Neuroptera with membranous wings but no sting; and the Hymenoptera, with membranous wings and a sting.
Jean-Baptiste de Lamarck, in his 1809 Philosophie Zoologique, treated the insects as one of nine invertebrate phyla. In his 1817 Le Règne Animal, Georges Cuvier grouped all animals into four embranchements ("branches" with different body plans), one of which was the articulated animals, containing arthropods and annelids. This arrangement was followed by the embryologist Karl Ernst von Baer in 1828, the zoologist Louis Agassiz in 1857, and the comparative anatomist Richard Owen in 1860. In 1874, Ernst Haeckel divided the animal kingdom into two subkingdoms, one of which was Metazoa for the multicellular animals. It had five phyla, including the articulates.
Modern
See also: Category:Insect orders and Category:Insect familiesTraditional morphology-based systematics have usually given the Hexapoda the rank of superclass, and identified four groups within it: insects (Ectognatha), Collembola, Protura, and Diplura, the latter three being grouped together as the Entognatha on the basis of internalized mouth parts.
The use of phylogenetic data has brought about numerous changes in relationships above the level of orders. Insects can be divided into two groups historically treated as subclasses: wingless insects or Apterygota, and winged insects or Pterygota. The Apterygota traditionally consisted of the primitively wingless orders Archaeognatha (jumping bristletails) and Zygentoma (silverfish). However, Apterygota is not monophyletic, as Archaeognatha are sister to all other insects, based on the arrangement of their mandibles, while the Pterygota, the winged insects, emerged from within the Dicondylia, alongside the Zygentoma.
The Pterygota (Palaeoptera and Neoptera) are winged and have hardened plates on the outside of their body segments; the Neoptera have muscles that allow their wings to fold flat over the abdomen. Neoptera can be divided into groups with incomplete metamorphosis (Polyneoptera and Paraneoptera) and those with complete metamorphosis (Holometabola). The molecular finding that the traditional louse orders Mallophaga and Anoplura are within Psocoptera has led to the new taxon Psocodea. Phasmatodea and Embiidina have been suggested to form the Eukinolabia. Mantodea, Blattodea, and Isoptera form a monophyletic group, Dictyoptera. Fleas are now thought to be closely related to boreid mecopterans.
Evolutionary history
Main article: Evolution of insectsThe oldest fossil that may be a primitive wingless insect is Leverhulmia from the Early Devonian Windyfield chert. The oldest known flying insects are from the mid-Carboniferous, around 328–324 million years ago. The group subsequently underwent a rapid explosive diversification. Claims that they originated substantially earlier, during the Silurian or Devonian (some 400 million years ago) based on molecular clock estimates, are unlikely to be correct, given the fossil record.
Four large-scale radiations of insects have occurred: beetles (from about 300 million years ago), flies (from about 250 million years ago), moths and wasps (both from about 150 million years ago).
The remarkably successful Hymenoptera (wasps, bees, and ants) appeared some 200 million years ago in the Triassic period, but achieved their wide diversity more recently in the Cenozoic era, which began 66 million years ago. Some highly successful insect groups evolved in conjunction with flowering plants, a powerful illustration of coevolution. Insects were among the earliest terrestrial herbivores and acted as major selection agents on plants. Plants evolved chemical defenses against this herbivory and the insects, in turn, evolved mechanisms to deal with plant toxins. Many insects make use of these toxins to protect themselves from their predators. Such insects often advertise their toxicity using warning colors.
- The giant dragonfly-like insect Meganeura monyi grew to wingspans of 75 cm (2 ft 6 in) in the late Carboniferous, around 300 million years ago.
- Beetle Moravocoleus permianus, fossil and reconstruction, from the Early Permian
- Hymenoptera such as this Iberomaimetsha from the Early Cretaceous, around 100 million years ago.
Morphology and physiology
Main article: Insect morphologyExternal
Three-part body
Insects have a segmented body supported by an exoskeleton, the hard outer covering made mostly of chitin. The body is organized into three interconnected units: the head, thorax and abdomen. The head supports a pair of sensory antennae, a pair of compound eyes, zero to three simple eyes (or ocelli) and three sets of variously modified appendages that form the mouthparts. The thorax carries the three pairs of legs and up to two pairs of wings. The abdomen contains most of the digestive, respiratory, excretory and reproductive structures.
Segmentation
Further information: Insect morphologyThe head is enclosed in a hard, heavily sclerotized, unsegmented head capsule, which contains most of the sensing organs, including the antennae, compound eyes, ocelli, and mouthparts. The thorax is composed of three sections named (from front to back) the prothorax, mesothorax and metathorax. The prothorax carries the first pair of legs. The mesothorax carries the second pair of legs and the front wings. The metathorax carries the third pair of legs and the hind wings. The abdomen is the largest part of the insect, typically with 11–12 segments, and is less strongly sclerotized than the head or thorax. Each segment of the abdomen has sclerotized upper and lower plates (the tergum and sternum), connected to adjacent sclerotized parts by membranes. Each segment carries a pair of spiracles.
Exoskeleton
Main article: Arthropod cuticleThe outer skeleton, the cuticle, is made up of two layers: the epicuticle, a thin and waxy water-resistant outer layer without chitin, and a lower layer, the thick chitinous procuticle. The procuticle has two layers: an outer exocuticle and an inner endocuticle. The tough and flexible endocuticle is built from numerous layers of fibrous chitin and proteins, criss-crossing each other in a sandwich pattern, while the exocuticle is rigid and sclerotized. As an adaptation to life on land, insects have an enzyme that uses atmospheric oxygen to harden their cuticle, unlike crustaceans which use heavy calcium compounds for the same purpose. This makes the insect exoskeleton a lightweight material.
Internal systems
Main article: Insect physiologyNervous
The nervous system of an insect consists of a brain and a ventral nerve cord. The head capsule is made up of six fused segments, each with either a pair of ganglia, or a cluster of nerve cells outside of the brain. The first three pairs of ganglia are fused into the brain, while the three following pairs are fused into a structure of three pairs of ganglia under the insect's esophagus, called the subesophageal ganglion. The thoracic segments have one ganglion on each side, connected into a pair per segment. This arrangement is also seen in the first eight segments of the abdomen. Many insects have fewer ganglia than this. Insects are capable of learning.
Digestive
An insect uses its digestive system to extract nutrients and other substances from the food it consumes. There is extensive variation among different orders, life stages, and even castes in the digestive system of insects. The gut runs lengthwise through the body. It has three sections, with paired salivary glands and salivary reservoirs. By moving its mouthparts the insect mixes its food with saliva. Some insects, like flies, expel digestive enzymes onto their food to break it down, but most insects digest their food in the gut. The foregut is lined with cuticule as protection from tough food. It includes the mouth, pharynx, and crop which stores food. Digestion starts in the mouth with enzymes in the saliva. Strong muscles in the pharynx pump fluid into the mouth, lubricating the food, and enabling certain insects to feed on blood or from the xylem and phloem transport vessels of plants. Once food leaves the crop, it passes to the midgut, where the majority of digestion takes place. Microscopic projections, microvilli, increase the surface area of the wall to absorb nutrients. In the hindgut, undigested food particles are joined by uric acid to form fecal pellets; most of the water is absorbed, leaving a dry pellet to be eliminated. Insects may have one to hundreds of Malpighian tubules. These remove nitrogenous wastes from the hemolymph of the insect and regulate osmotic balance. Wastes and solutes are emptied directly into the alimentary canal, at the junction between the midgut and hindgut.
Reproductive
Main article: Insect reproductive systemThe reproductive system of female insects consist of a pair of ovaries, accessory glands, one or more spermathecae to store sperm, and ducts connecting these parts. The ovaries are made up of a variable number of egg tubes, ovarioles. Female insects make eggs, receive and store sperm, manipulate sperm from different males, and lay eggs. Accessory glands produce substances to maintain sperm and to protect the eggs. They can produce glue and protective substances for coating eggs, or tough coverings for a batch of eggs called oothecae.
For males, the reproductive system consists of one or two testes, suspended in the body cavity by tracheae. The testes contain sperm tubes or follicles in a membranous sac. These connect to a duct that leads to the outside. The terminal portion of the duct may be sclerotized to form the intromittent organ, the aedeagus.
Respiratory
Main article: Respiratory system of insectsInsect respiration is accomplished without lungs. Instead, insects have a system of internal tubes and sacs through which gases either diffuse or are actively pumped, delivering oxygen directly to tissues that need it via their tracheae and tracheoles. In most insects, air is taken in through paired spiracles, openings on the sides of the abdomen and thorax. The respiratory system limits the size of insects. As insects get larger, gas exchange via spiracles becomes less efficient, and thus the heaviest insect currently weighs less than 100 g. However, with increased atmospheric oxygen levels, as were present in the late Paleozoic, larger insects were possible, such as dragonflies with wingspans of more than two feet (60 cm). Gas exchange patterns in insects range from continuous and diffusive ventilation, to discontinuous.
Circulatory
Further information: Insect physiology § Circulatory systemBecause oxygen is delivered directly to tissues via tracheoles, the circulatory system is not used to carry oxygen, and is therefore greatly reduced. The insect circulatory system is open; it has no veins or arteries, and instead consists of little more than a single, perforated dorsal tube that pulses peristaltically. This dorsal blood vessel is divided into two sections: the heart and aorta. The dorsal blood vessel circulates the hemolymph, arthropods' fluid analog of blood, from the rear of the body cavity forward. Hemolymph is composed of plasma in which hemocytes are suspended. Nutrients, hormones, wastes, and other substances are transported throughout the insect body in the hemolymph. Hemocytes include many types of cells that are important for immune responses, wound healing, and other functions. Hemolymph pressure may be increased by muscle contractions or by swallowing air into the digestive system to aid in molting.
Sensory
Further information: Insect physiology § Sensory organsMany insects possess numerous specialized sensory organs able to detect stimuli including limb position (proprioception) by campaniform sensilla, light, water, chemicals (senses of taste and smell), sound, and heat. Some insects such as bees can perceive ultraviolet wavelengths, or detect polarized light, while the antennae of male moths can detect the pheromones of female moths over distances of over a kilometer. There is a trade-off between visual acuity and chemical or tactile acuity, such that most insects with well-developed eyes have reduced or simple antennae, and vice versa. Insects perceive sound by different mechanisms, such as thin vibrating membranes (tympana). Insects were the earliest organisms to produce and sense sounds. Hearing has evolved independently at least 19 times in different insect groups.
Most insects, except some cave crickets, are able to perceive light and dark. Many have acute vision capable of detecting small and rapid movements. The eyes may include simple eyes or ocelli as well as larger compound eyes. Many species can detect light in the infrared, ultraviolet and visible light wavelengths, with color vision. Phylogenetic analysis suggests that UV-green-blue trichromacy existed from at least the Devonian period, some 400 million years ago.
The individual lenses in compound eyes are immobile, but fruit flies have photoreceptor cells underneath each lens which move rapidly in and out of focus, in a series of movements called photoreceptor microsaccades. This gives them, and possibly many other insects, a much clearer image of the world than previously assumed.
An insect's sense of smell is via chemical receptors, usually on the antennae and the mouthparts. These detect both airborne volatile compounds and odorants on surfaces, including pheromones from other insects and compounds released by food plants. Insects use olfaction to locate mating partners, food, and places to lay eggs, and to avoid predators. It is thus an extremely important sense, enabling insects to discriminate between thousands of volatile compounds.
Some insects are capable of magnetoreception; ants and bees navigate using it both locally (near their nests) and when migrating. The Brazilian stingless bee detects magnetic fields using the hair-like sensilla on its antennae.
Reproduction and development
Life-cycles
The majority of insects hatch from eggs. The fertilization and development takes place inside the egg, enclosed by a shell (chorion) that consists of maternal tissue. In contrast to eggs of other arthropods, most insect eggs are drought resistant. This is because inside the chorion two additional membranes develop from embryonic tissue, the amnion and the serosa. This serosa secretes a cuticle rich in chitin that protects the embryo against desiccation. Some species of insects, like aphids and tsetse flies, are ovoviviparous: their eggs develop entirely inside the female, and then hatch immediately upon being laid. Some other species, such as in the cockroach genus Diploptera, are viviparous, gestating inside the mother and born alive. Some insects, like parasitoid wasps, are polyembryonic, meaning that a single fertilized egg divides into many separate embryos. Insects may be univoltine, bivoltine or multivoltine, having one, two or many broods in a year.
Other developmental and reproductive variations include haplodiploidy, polymorphism, paedomorphosis or peramorphosis, sexual dimorphism, parthenogenesis, and more rarely hermaphroditism. In haplodiploidy, which is a type of sex-determination system, the offspring's sex is determined by the number of sets of chromosomes an individual receives. This system is typical in bees and wasps.
Some insects are parthenogenetic, meaning that the female can reproduce and give birth without having the eggs fertilized by a male. Many aphids undergo a cyclical form of parthenogenesis in which they alternate between one or many generations of asexual and sexual reproduction. In summer, aphids are generally female and parthenogenetic; in the autumn, males may be produced for sexual reproduction. Other insects produced by parthenogenesis are bees, wasps and ants; in their haplodiploid system, diploid females spawn many females and a few haploid males.
Metamorphosis
Metamorphosis in insects is the process of development that converts young to adults. There are two forms of metamorphosis: incomplete and complete.
Incomplete
Main article: HemimetabolismHemimetabolous insects, those with incomplete metamorphosis, change gradually after hatching from the egg by undergoing a series of molts through stages called instars, until the final, adult, stage is reached. An insect molts when it outgrows its exoskeleton, which does not stretch and would otherwise restrict the insect's growth. The molting process begins as the insect's epidermis secretes a new epicuticle inside the old one. After this new epicuticle is secreted, the epidermis releases a mixture of enzymes that digests the endocuticle and thus detaches the old cuticle. When this stage is complete, the insect makes its body swell by taking in a large quantity of water or air; this makes the old cuticle split along predefined weaknesses where it was thinnest.
Complete
Main article: HolometabolismHolometabolism, or complete metamorphosis, is where the insect changes in four stages, an egg or embryo, a larva, a pupa and the adult or imago. In these species, an egg hatches to produce a larva, which is generally worm-like in form. This can be eruciform (caterpillar-like), scarabaeiform (grub-like), campodeiform (elongated, flattened and active), elateriform (wireworm-like) or vermiform (maggot-like). The larva grows and eventually becomes a pupa, a stage marked by reduced movement. There are three types of pupae: obtect, exarate or coarctate. Obtect pupae are compact, with the legs and other appendages enclosed. Exarate pupae have their legs and other appendages free and extended. Coarctate pupae develop inside the larval skin. Insects undergo considerable change in form during the pupal stage, and emerge as adults. Butterflies are well-known for undergoing complete metamorphosis; most insects use this life cycle. Some insects have evolved this system to hypermetamorphosis. Complete metamorphosis is a trait of the most diverse insect group, the Endopterygota.
Communication
Insects that produce sound can generally hear it. Most insects can hear only a narrow range of frequencies related to the frequency of the sounds they can produce. Mosquitoes can hear up to 2 kilohertz. Certain predatory and parasitic insects can detect the characteristic sounds made by their prey or hosts, respectively. Likewise, some nocturnal moths can perceive the ultrasonic emissions of bats, which helps them avoid predation.
Light production
A few insects, such as Mycetophilidae (Diptera) and the beetle families Lampyridae, Phengodidae, Elateridae and Staphylinidae are bioluminescent. The most familiar group are the fireflies, beetles of the family Lampyridae. Some species are able to control this light generation to produce flashes. The function varies with some species using them to attract mates, while others use them to lure prey. Cave dwelling larvae of Arachnocampa (Mycetophilidae, fungus gnats) glow to lure small flying insects into sticky strands of silk. Some fireflies of the genus Photuris mimic the flashing of female Photinus species to attract males of that species, which are then captured and devoured. The colors of emitted light vary from dull blue (Orfelia fultoni, Mycetophilidae) to the familiar greens and the rare reds (Phrixothrix tiemanni, Phengodidae).
Sound production
Insects make sounds mostly by mechanical action of appendages. In grasshoppers and crickets, this is achieved by stridulation. Cicadas make the loudest sounds among the insects by producing and amplifying sounds with special modifications to their body to form tymbals and associated musculature. The African cicada Brevisana brevis has been measured at 106.7 decibels at a distance of 50 cm (20 in). Some insects, such as the Helicoverpa zea moths, hawk moths and Hedylid butterflies, can hear ultrasound and take evasive action when they sense that they have been detected by bats. Some moths produce ultrasonic clicks that warn predatory bats of their unpalatability (acoustic aposematism), while some palatable moths have evolved to mimic these calls (acoustic Batesian mimicry). The claim that some moths can jam bat sonar has been revisited. Ultrasonic recording and high-speed infrared videography of bat-moth interactions suggest the palatable tiger moth really does defend against attacking big brown bats using ultrasonic clicks that jam bat sonar.
Grasshopper stridulation Several unidentified grasshoppers stridulatingProblems playing this file? See media help.
Very low sounds are produced in various species of Coleoptera, Hymenoptera, Lepidoptera, Mantodea and Neuroptera. These low sounds are produced by the insect's movement, amplified by stridulatory structures on the insect's muscles and joints; these sounds can be used to warn or communicate with other insects. Most sound-making insects also have tympanal organs that can perceive airborne sounds. Some hemipterans, such as the water boatmen, communicate via underwater sounds.
Communication using surface-borne vibrational signals is more widespread among insects because of size constraints in producing air-borne sounds. Insects cannot effectively produce low-frequency sounds, and high-frequency sounds tend to disperse more in a dense environment (such as foliage), so insects living in such environments communicate primarily using substrate-borne vibrations.
Some species use vibrations for communicating, such as to attract mates as in the songs of the shield bug Nezara viridula. Vibrations can also be used to communicate between species; lycaenid caterpillars, which form a mutualistic association with ants communicate with ants in this way. The Madagascar hissing cockroach has the ability to press air through its spiracles to make a hissing noise as a sign of aggression; the death's-head hawkmoth makes a squeaking noise by forcing air out of their pharynx when agitated, which may also reduce aggressive worker honey bee behavior when the two are close.
Chemical communication
Main articles: Chemical communication in insects and Insect olfactionMany insects have evolved chemical means for communication. These semiochemicals are often derived from plant metabolites including those meant to attract, repel and provide other kinds of information. Pheromones are used for attracting mates of the opposite sex, for aggregating conspecific individuals of both sexes, for deterring other individuals from approaching, to mark a trail, and to trigger aggression in nearby individuals. Allomones benefit their producer by the effect they have upon the receiver. Kairomones benefit their receiver instead of their producer. Synomones benefit the producer and the receiver. While some chemicals are targeted at individuals of the same species, others are used for communication across species. The use of scents is especially well-developed in social insects. Cuticular hydrocarbons are nonstructural materials produced and secreted to the cuticle surface to fight desiccation and pathogens. They are important, too, as pheromones, especially in social insects.
Social behavior
Main article: Eusociality A cathedral mound created by eusocial mound-building termites.Honey bee's figure-eight waggle dance. An orientation 45° to the right of ‘up' on the comb indicates food 45° to the right of the sun. The dancer's rapid waggling blurs her abdomen.Social insects, such as termites, ants and many bees and wasps, are eusocial. They live together in such large well-organized colonies of genetically similar individuals that they are sometimes considered superorganisms. In particular, reproduction is largely limited to a queen caste; other females are workers, prevented from reproducing by worker policing. Honey bees have evolved a system of abstract symbolic communication where a behavior is used to represent and convey specific information about the environment. In this communication system, called dance language, the angle at which a bee dances represents a direction relative to the sun, and the length of the dance represents the distance to be flown. Bumblebees too have some social communication behaviors. Bombus terrestris, for example, more rapidly learns about visiting unfamiliar, yet rewarding flowers, when they can see a conspecific foraging on the same species.
Only insects that live in nests or colonies possess fine-scale spatial orientation. Some can navigate unerringly to a single hole a few millimeters in diameter among thousands of similar holes, after a trip of several kilometers. In philopatry, insects that hibernate are able to recall a specific location up to a year after last viewing the area of interest. A few insects seasonally migrate large distances between different geographic regions, as in the continent-wide monarch butterfly migration.
Care of young
Eusocial insects build nests, guard eggs, and provide food for offspring full-time. Most insects, however, lead short lives as adults, and rarely interact with one another except to mate or compete for mates. A small number provide parental care, where they at least guard their eggs, and sometimes guard their offspring until adulthood, possibly even feeding them. Many wasps and bees construct a nest or burrow, store provisions in it, and lay an egg upon those provisions, providing no further care.
Locomotion
Flight
Main article: Insect flightInsects are the only group of invertebrates to have developed flight. The ancient groups of insects in the Palaeoptera, the dragonflies, damselflies and mayflies, operate their wings directly by paired muscles attached to points on each wing base that raise and lower them. This can only be done at a relatively slow rate. All other insects, the Neoptera, have indirect flight, in which the flight muscles cause rapid oscillation of the thorax: there can be more wingbeats than nerve impulses commanding the muscles. One pair of flight muscles is aligned vertically, contracting to pull the top of the thorax down, and the wings up. The other pair runs longitudinally, contracting to force the top of the thorax up and the wings down. Most insects gain aerodynamic lift by creating a spiralling vortex at the leading edge of the wings. Small insects like thrips with tiny feathery wings gain lift using the clap and fling mechanism; the wings are clapped together and pulled apart, flinging vortices into the air at the leading edges and at the wingtips.
The evolution of insect wings has been a subject of debate; it has been suggested they came from modified gills, flaps on the spiracles, or an appendage, the epicoxa, at the base of the legs. More recently, entomologists have favored evolution of wings from lobes of the notum, of the pleuron, or more likely both. In the Carboniferous age, the dragonfly-like Meganeura had as much as a 50 cm (20 in) wide wingspan. The appearance of gigantic insects is consistent with high atmospheric oxygen at that time, as the respiratory system of insects constrains their size. The largest flying insects today are much smaller, with the largest wingspan belonging to the white witch moth (Thysania agrippina), at approximately 28 cm (11 in).
Unlike birds, small insects are swept along by the prevailing winds although many larger insects migrate. Aphids are transported long distances by low-level jet streams.
Walking
Further information: Walking § InsectsMany adult insects use six legs for walking, with an alternating tripod gait. This allows for rapid walking with a stable stance; it has been studied extensively in cockroaches and ants. For the first step, the middle right leg and the front and rear left legs are in contact with the ground and move the insect forward, while the front and rear right leg and the middle left leg are lifted and moved forward to a new position. When they touch the ground to form a new stable triangle, the other legs can be lifted and brought forward in turn. The purest form of the tripedal gait is seen in insects moving at high speeds. However, this type of locomotion is not rigid and insects can adapt a variety of gaits. For example, when moving slowly, turning, avoiding obstacles, climbing or slippery surfaces, four (tetrapodal) or more feet (wave-gait) may be touching the ground. Cockroaches are among the fastest insect runners and, at full speed, adopt a bipedal run. More sedate locomotion is seen in the well-camouflaged stick insects (Phasmatodea). A small number of species such as Water striders can move on the surface of water; their claws are recessed in a special groove, preventing the claws from piercing the water's surface film. The ocean-skaters in the genus Halobates even live on the surface of open oceans, a habitat that has few insect species.
Swimming
Main article: Aquatic insectsA large number of insects live either part or the whole of their lives underwater. In many of the more primitive orders of insect, the immature stages are aquatic. In some groups, such as water beetles, the adults too are aquatic.
Many of these species are adapted for under-water locomotion. Water beetles and water bugs have legs adapted into paddle-like structures. Dragonfly naiads use jet propulsion, forcibly expelling water out of their rectal chamber. Other insects such as the rove beetle Stenus emit pygidial gland surfactant secretions that reduce surface tension; this enables them to move on the surface of water by Marangoni propulsion.
Ecology
Main article: Insect ecologyInsects play many critical roles in ecosystems, including soil turning and aeration, dung burial, pest control, pollination and wildlife nutrition. For instance, termites modify the environment around their nests, encouraging grass growth; many beetles are scavengers; dung beetles recycle biological materials into forms useful to other organisms. Insects are responsible for much of the process by which topsoil is created.
Defense
Main article: Defense in insectsInsects are mostly small, soft bodied, and fragile compared to larger lifeforms. The immature stages are small, move slowly or are immobile, and so all stages are exposed to predation and parasitism. Insects accordingly employ multiple defensive strategies, including camouflage, mimicry, toxicity and active defense. Many insects rely on camouflage to avoid being noticed by their predators or prey. It is common among leaf beetles and weevils that feed on wood or vegetation. Stick insects mimic the forms of sticks and leaves. Many insects use mimicry to deceive predators into avoiding them. In Batesian mimicry, edible species, such as of hoverflies (the mimics), gain a survival advantage by resembling inedible species (the models). In Müllerian mimicry, inedible species, such as of wasps and bees, resemble each other so as to reduce the sampling rate by predators who need to learn that those insects are inedible. Heliconius butterflies, many of which are toxic, form Müllerian complexes, advertising their inedibility. Chemical defense is common among Coleoptera and Lepidoptera, usually being advertised by bright warning colors (aposematism), as in the monarch butterfly. As larvae, they obtain their toxicity by sequestering chemicals from the plants they eat into their own tissues. Some manufacture their own toxins. Predators that eat poisonous butterflies and moths may vomit violently, learning not to eat insects with similar markings; this is the basis of Müllerian mimicry. Some ground beetles of the family Carabidae actively defend themselves, spraying chemicals from their abdomen with great accuracy, to repel predators.
Pollination
Main article: EntomophilyPollination is the process by which pollen is transferred in the reproduction of plants, thereby enabling fertilisation and sexual reproduction. Most flowering plants require an animal to do the transportation. The majority of pollination is by insects. Because insects usually receive benefit for the pollination in the form of energy rich nectar it is a mutualism. The various flower traits, such as bright colors and pheromones that coevolved with their pollinators, have been called pollination syndromes, though around one third of flowers cannot be assigned to a single syndrome.
Parasitism
Further information: Parasitism and Parasitoid waspMany insects are parasitic. The largest group, with over 100,000 species and perhaps over a million, consists of a single clade of parasitoid wasps among the Hymenoptera. These are parasites of other insects, eventually killing their hosts. Some are hyper-parasites, as their hosts are other parasitoid wasps. Several groups of insects can be considered as either micropredators or external parasites; for example, many hemipteran bugs have piercing and sucking mouthparts, adapted for feeding on plant sap, while species in groups such as fleas, lice, and mosquitoes are hematophagous, feeding on the blood of animals.
- A parasitoid wasp ovipositing into an aphid
- Plant parasite or micropredator: a coreid bug sucking plant sap
- Human head-lice are directly transmitted obligate ectoparasites.
Relationship to humans
Main article: Human interactions with insectsAs pests
Main article: Pest insectMany insects are considered pests by humans. These include parasites of people and livestock, such as lice and bed bugs; mosquitoes act as vectors of several diseases. Other pests include insects like termites that damage wooden structures; herbivorous insects such as locusts, aphids, and thrips that destroy agricultural crops, or like wheat weevils damage stored agricultural produce. Farmers have often attempted to control insects with chemical insecticides, but increasingly rely on biological pest control. This uses one organism to reduce the population density of a pest organism; it is a key element of integrated pest management. Biological control is favored because insecticides can cause harm to ecosystems far beyond the intended pest targets.
In beneficial roles
See also: Economic entomology § Beneficial insectsPollination of flowering plants by insects including bees, butterflies, flies, and beetles, is economically important. The value of insect pollination of crops and fruit trees was estimated in 2021 to be about $34 billion in the US alone.
Insects produce useful substances such as honey, wax, lacquer and silk. Honey bees have been cultured by humans for thousands of years for honey. Beekeeping in pottery vessels began about 9,000 years ago in North Africa. The silkworm has greatly affected human history, as silk-driven trade established relationships between China and the rest of the world.
Insects that feed on or parasitise other insects are beneficial to humans if they thereby reduce damage to agriculture and human structures. For example, aphids feed on crops, causing economic loss, but ladybugs feed on aphids, and can be used to control them. Insects account for the vast majority of insect consumption.
Fly larvae (maggots) were formerly used to treat wounds to prevent or stop gangrene, as they would only consume dead flesh. This treatment is finding modern usage in some hospitals. Insects have gained attention as potential sources of drugs and other medicinal substances. Adult insects, such as crickets and insect larvae of various kinds, are commonly used as fishing bait.
Population declines
Main article: Decline in insect populationsAt least 66 insect species extinctions have been recorded since 1500, many of them on oceanic islands. Declines in insect abundance have been attributed to human activity in the form of artificial lighting, land use changes such as urbanization or farming, pesticide use, and invasive species. A 2019 research review suggested that a large proportion of insect species is threatened with extinction in the 21st century, though the details have been disputed. A larger 2020 meta-study, analyzing data from 166 long-term surveys, suggested that populations of terrestrial insects are indeed decreasing rapidly, by about 9% per decade.
In research
Insects play important roles in biological research. For example, because of its small size, short generation time and high fecundity, the common fruit fly Drosophila melanogaster is a model organism for studies in the genetics of eukaryotes, including genetic linkage, interactions between genes, chromosomal genetics, development, behavior and evolution. Because genetic systems are well conserved among eukaryotes, understanding basic cellular processes like DNA replication or transcription in fruit flies can help to understand those processes in other eukaryotes, including humans. The genome of D. melanogaster was sequenced in 2000, reflecting the organism's important role in biological research. It was found that 70% of the fly genome is similar to the human genome, supporting the theory of evolution.
As food
Main article: Insects as foodInsects are consumed as food in 80% of the world's nations, by people in roughly 3,000 ethnic groups. In Africa, locally abundant species of locusts and termites are a common traditional human food source. Some, especially deep-fried cicadas, are considered to be delicacies. Insects have a high protein content for their mass, and some authors suggest their potential as a major source of protein in human nutrition. In most first-world countries, however, entomophagy (the eating of insects), is taboo. They are also recommended by armed forces as a survival food for troops in adversity. Because of the abundance of insects and a worldwide concern of food shortages, the Food and Agriculture Organization of the United Nations considers that people throughout the world may have to eat insects as a food staple. Insects are noted for their nutrients, having a high content of protein, minerals and fats and are already regularly eaten by one-third of the world's population.
In other products
Black soldier fly larvae can provide protein and fats for use in cosmetics. Insect cooking oil, insect butter and fatty alcohols can be made from such insects as the superworm (Zophobas morio). Insect species including the black soldier fly or the housefly in their maggot forms, and beetle larvae such as mealworms, can be processed and used as feed for farmed animals including chicken, fish and pigs. Many species of insects are sold and kept as pets.
In religion and folklore
Further information: Insects in mythologyScarab beetles held religious and cultural symbolism in ancient Egypt, Greece and some shamanistic Old World cultures. The ancient Chinese regarded cicadas as symbols of rebirth or immortality. In Mesopotamian literature, the epic poem of Gilgamesh has allusions to Odonata that signify the impossibility of immortality. Among the Aborigines of Australia of the Arrernte language groups, honey ants and witchetty grubs served as personal clan totems. In the case of the 'San' bush-men of the Kalahari, it is the praying mantis that holds much cultural significance including creation and zen-like patience in waiting.
See also
Notes
- The Museum of New Zealand notes that "in everyday conversation", bug "refers to land arthropods with at least six legs, such as insects, spiders, and centipedes". In a chapter on "Bugs That Are Not Insects", entomologist Gilbert Walbauer specifies centipedes, millipedes, arachnids (spiders, daddy longlegs, scorpions, mites, chiggers and ticks) as well as the few terrestrial crustaceans (sowbugs and pillbugs).
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- Ramos-Elorduy, Julieta; Menzel, Peter (1998). Creepy crawly cuisine: the gourmet guide to edible insects. Inner Traditions / Bear & Company. p. 44. ISBN 978-0-89281-747-4. Retrieved 23 April 2014.
- ^ "Insects as Food for Humans". Retrieved 14 September 2022.
- Gullan & Cranston 2005, pp. 10–13.
- Michels, John (1880). John Michels (ed.). Science. Vol. 1. New York: American Association for the Advance of Science. p. 69.
- Maierbrugger, Arno (14 May 2013). "UN: Insects are 'food of the future' (video)". Inside Investor. Archived from the original on 10 September 2013. Retrieved 17 May 2013.
- Verheyen, Geert; Ooms, Tom; Vogels, Liesbeth; Vreysen, Steven; Bovy, Ann; Van Miert, Sabine; Meersman, Filip (1 May 2018). "Insects as an Alternative Source for the Production of Fats for Cosmetics". Journal of Cosmetic Science. 69 (3): 187–202. PMID 30052193.
- "From Pest to Pot: Can Insects Feed the World?". National Geographic Culture. 15 August 2016. Archived from the original on 10 April 2021. Retrieved 13 January 2022.
- "How AgriProtein makes chicken food from maggots". Wired UK. Retrieved 13 January 2022.
- Bugs. "Bugs – das Wirbellosenmagazin". NTV Verlag. Retrieved 7 March 2021.
- Gullan & Cranston 2005, p. 9.
Sources
- Gullan, P. J.; Cranston, P. S. (2005). The Insects: An Outline of Entomology (3rd ed.). Oxford: Blackwell Publishing. ISBN 978-1-4051-1113-3.
- Gullan, P. J.; Cranston, P. S. (2014). The Insects: An Outline of Entomology (5th ed.). Oxford: Wiley Blackwell. ISBN 978-1-118-84616-2.
- Nation, James L. (2001). Insect Physiology and Biochemistry (1st ed.). CRC Press. ISBN 978-0-8493-1181-9.
- Resh, Vincent H.; Carde, Ring T. (2009). Encyclopedia of Insects (2 ed.). Academic Press. ISBN 978-0-12-374144-8.
- Schowalter, Timothy Duane (2006). Insect Ecology: An Ecosystem Epproach (2nd (illustrated) ed.). Academic Press. ISBN 978-0-12-088772-9. Archived from the original on 3 June 2016. Retrieved 27 October 2015.
External links
Listen to this article (5 minutes) This audio file was created from a revision of this article dated 30 October 2010 (2010-10-30), and does not reflect subsequent edits.(Audio help · More spoken articles)- Insect species and observations on iNaturalist
- Overview of Orders of Insects
- "Insect". The Encyclopedia of Life.
- A Safrinet Manual for Entomology and Arachnology SPC
- Tree of Life Project – Insecta, Insecta Movies
- Fossil Insect Database: Holotypes at the International Palaeoentological Society
- UF Book of Insect Records
- InsectImages.org 24,000 high resolution insect photographs
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