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Weta
Male Wellington tree weta
Scientific classification
Kingdom:	Animalia
Phylum:	Arthropoda
Class:	Insecta
Order:	Orthoptera
Suborder:	Ensifera
Superfamily:	Stenopelmatoidea, Rhaphidophoroidea
Family:	Anostostomatidae, Rhaphidophoridae

Weta is the name given to about 70 insect species endemic to New Zealand. Many similar species occur around the world, though most are in the Southern Hemisphere. The name comes from the Māori word wētā, and (as with all Māori words) is the same in the plural (like 'sheep'). The Māori word for the giant weta is wētā punga (lumpy or jointed weta).

New Zealand visual effects houses Weta Workshop and Weta Digital were named after the insect.

General characteristics

Many weta are large by insect standards and some species are among the largest and heaviest in the world able to fly. Their physical appearance is like a katydid, long-horned grasshopper, or cricket, but the hind legs are enlarged and usually very spiny. Many are wingless. Because they can cope with variations in temperature, weta are found in a variety of environments, including alpine, forests, grasslands, caves, shrub lands and urban gardens. They are nocturnal, and all New Zealand species are flightless. Different species have different diets. Most weta are predators or omnivores preying on other invertebrates, but the tree and giant weta eat mostly lichens, leaves, flowers, seed-heads and fruit.

Weta can bite with powerful mandibles. Tree weta bites are painful but not particularly common. Weta can inflict painful scratches, with the potential of infection, but their defence displays consist of looking large and spiky, and they will retreat if given a chance. Tree weta arc their hind legs into the air in warning to foes, and then strike downwards, so the spines could scratch the eyes of a predator. Pegs or ridges at the base of the abdomen are struck by a patch of fine pegs at the base (inner surface) of the legs and this action makes a distinctive sound. These actions are also used in defence of a gallery by competing males. The female weta looks as if she has a stinger, but it is an ovipositor, which enables her to lay eggs inside rotting wood or soil. Some species of Hemiandrus have very short ovipositors, related perhaps to their burrowing into soil and laying their eggs in a special chamber at the end of the burrow.

New Zealand had no land mammals (apart from native bats) before humans arrived, and ecological niches occupied by mammals in other parts of the world were taken by nonmammals. The weta’s place in the ecosystem is comparable to that held by mice and other rodents elsewhere in the world. For example, they are hunted by an owl, the morepork, New Zealand’s only surviving native owl. Weta pass seeds of some plant species through their digestive tracts unharmed, thus acting as effective seed dispersers. The effects of decreases in weta populations on native plant species that may rely on the weta's help are yet to be determined. The weta's lifestyle and habitat, where it may choose to remain concealed in suburban environments until unexpectedly confronted, combined with its notoriously unfriendly appearance, make it a frequent victim of irrational human aggression.

Taxonomy and evolution

Fossilized orthopterans have been found in Russia, China, South Africa, Australia and New Zealand, but the relationships are very open to different interpretations. Certainly, most weta of both families are in the Southern Hemisphere lands. Pratt, Morgan-Richards and Trewick think weta were present in ancient Gondwanaland before New Zealand separated from it, although they possibly dispersed as they must have done so to colonise New Caledonia and the Chatham Islands. Although they are of an ancient lineage, the present species are quite young, which conflicts with those earlier ideas about dispersal of weta forebears around the Southern Hemisphere (Wallis et al. 2000).

Giant, tree, ground, and tusked weta are all members of the family Anostostomatidae (formerly in the Stenopelmatidae, but recently separated (Johns, 1997)). Cave weta are members of the family Rhaphidophoridae called cave crickets or camel crickets elsewhere, in a different ensiferan superfamily.

Lifecycle

Tree weta eggs are laid over the autumn and winter months and hatch the following spring. A tree weta takes between one and two years to reach adulthood, and over this time will have to shed its skin around ten times as it grows.

Giant weta

The 11 species of giant weta (Deinacrida spp.), most significantly larger than other weta, are themselves large by insect standards. They are heavy insects with a body length of up to 100 mm (4 in) excluding their lengthy legs and antennae, and weigh about 20–30 g. A captive giant weta (Deinacrida heteracantha) filled with eggs reached a record 70 g, making it one of the heaviest documented insects in the world and heavier than a sparrow. The largest species of giant weta is the Little Barrier Island weta, also known as the wetapunga. Giant weta tend to be less social and more passive than other weta. They are classified in the genus Deinacrida, which is Greek for "terrible grasshopper". They are found primarily on small islands off the coast of the main islands, and are examples of island gigantism.

Tree weta

Tree weta (Hemideina) are those most commonly encountered in suburban settings in the North Island. They are up to 40 mm long and most commonly live in holes in trees formed by beetle and moth larvae or where rot has set in after a twig has broken off. The hole, called a gallery, is maintained by the weta and any growth of the bark surrounding the opening is chewed away. They readily occupy a preformed gallery in a piece of wood (a weta motel) and can be kept in a suburban garden as pets. A gallery might house a harem of up to 10 juveniles of both sexes, females and one male. Tree weta are nocturnal. Their diet consists of plants and small insects. The males have much larger jaws than the females, though both sexes will hiss and bite when threatened.

The seven species of tree weta are:

• The Auckland tree weta Hemideina thoracica (also called tokoriro) can be found throughout the North Island apart from the Wellington-Wairarapa region.
• The Wellington tree weta H. crassidens occupies Wellington, the Wairarapa, the northern parts of South Island, and the West Coast.
  • H. crassidens crassicruris was described from Stephens Island, but is now recognized as H. crassidens.
• H. trewicki is found in Hawke's Bay.
• H. femorata is found in Marlborough and Canterbury.
• The rare H. ricta species occurs in Banks Peninsula.
• The West Coast bush weta H. broughi largely overlaps with the Wellington tree weta in Nelson and the northern portion of the West Coast.
• H. maori, the mountain stone weta, lives in the drier areas of the South Island high country from the Kaikoura Ranges south to Rock and Pillar Range near Dunedin. At most sites, it lives on the ground, under stones or in crevices, but in at least two island (within lakes) sites which have not been modified greatly, it readily lives both in trees and on the ground.

Mountain stone weta can survive being frozen for months in a state of suspended animation down to temperatures of -10°C, because their haemolymph (the insect equivalent of blood) contains special proteins that prevent ice from forming in their cells. It also displays the defensive behaviour of "playing dead", by lying still for a short time on its back with legs splayed and claws exposed and jaws wide open ready to scratch and bite.

When the territories of species overlap, as with the related species H. femorata and H. ricta on Banks Peninsula, they may interbreed, although offspring are sterile.

Tusked weta

Tusked weta are distinctive because the males have long, curved tusks projecting forward from their jaws. The tusks are used to push an opponent; they are not used for biting. The females are similar to ground weta. Tusked weta are mainly carnivorous, eating worms and insects. They consist of three species: the Northland tusked weta Hemiandrus monstrosus, now named Anisoura nicobarica; the Middle Island tusked weta Motuweta isolata; and a newly discovered Raukumara tusked weta, Motuweta riparia. The Northland tusked weta lives in tree holes similar to tree weta. The Middle Island tusked weta, also called the Mercury Island tusked weta after the islands on which it lives, was discovered in 1970. It is a ground-dwelling weta, covering its shallow burrows with leaves. The Middle Island weta is the most endangered weta species, so a Department of Conservation breeding programme is establishing new colonies on other islands of the Mercury Island group. The Raukumara was discovered in 1996, in the Raukumara Range near the Bay of Plenty. Probably, more species are still to be identified.

Ground weta

Ground weta are classified in the genus Hemiandrus. About 40 species of ground weta occur in New Zealand, and several very similar ones are found in Australia. They are also very like the Californian Cnemotettix—a similarity perhaps due to their very similar habits and habitat. Most of the Hemiandrus have not been described. They hide in burrows in the ground during the day, and those that live in open ground (e.g., H. focalis) conceal their exit holes with a specially made perforated door. During the night, ground weta hunt invertebrate prey and eat fruit.

Cave weta

The 60 species of cave weta have extra-long antennae, and may have long, slender legs and a passive demeanour. Although they have no hearing organs on their front legs like species of Hemideina and Deinacrida, some (e.g., Talitropsis spp.) are very sensitive to ground vibrations sensed through pads on their feet. Specialised hairs on the cerci and organs on the antennae are also sensitive to low-frequency vibrations in the air. Cave weta may be active within the confines of their caves during the daytime, and those individuals close to cave entrances venture outside at night. But most species are forest dwellers and a few are to be found in the high alpine screes living among the broken rocks covered with snow up to six months of the year. The weta stay frozen until spring time. New Zealand species are classified in several genera in subfamily Macropathinae of family Rhaphidophoridae, and are very distant cousins of the other types of weta.

• Face
• Lower leg (tarsus) with two claws and sensory pads
• Upper leg
• Underside with parasites

Conservation

Although the weta had native predators in the form of birds (especially the weka and kiwi), reptiles, and bats before the arrival of humans, introduced species such as cats, hedgehogs, rats (including kiore) and mustelids have caused a sharp increase in the rate of predation. They are also vulnerable to habitat destruction caused by humans and modification of their habitat caused by introduced browsers. New Zealand’s Department of Conservation considers 16 of the 70 species at risk. Programmes to prevent extinctions have been implemented since the 1970s.

Some examples of especially endangered species are even tracked by radio beacons.

Notes

1. Because Punga is a mythological character associated with ugly creatures, wētā punga is sometimes rendered in English as 'god of ugly things'.

References

1. Kleinpaste, Ruud (1997). Scratching for a living. {{cite book}}: Cite has empty unknown parameter: |coauthors= (help)
2. Duthie, Catherine; Gibbs, George; Burns, K.C. (2006). "Seed Dispersal by Weta". Science. 311 (5767). American Association for the Advancement of Science: 1575. doi:10.1126/science.1123544.
3. Diversification of New Zealand weta (Orthoptera: Ensifera: Anostostomatidae) and their relationships in Australasia Philosophical Transactions of the Royal Society
4. "Story: Wētā". Te Ara - the Encyclopedia of New Zealand. Retrieved 4 September 2012.
5. "Book of Insect Records".
6. "Eel's costly snack". The New Zealand Herald. 16 May 2009. Retrieved 3 December 2011.

Further reading

• Johns, P. M. (1997). "The Gondwanaland weta: family Anostostomatidae (formerly in Stenopelmatidae, Henicidae or Mimnermidae): nomenclatural problems, world checklist, new genera and species". Journal of Orthoptera Research. 6 (6). Orthopterists' Society: 125–138. doi:10.2307/3503546. JSTOR 3503546. {{cite journal}}: Cite has empty unknown parameters: |month= and |coauthors= (help)
• Steve Trewick. "New Zealand Invertebrate Speciation". Archived from the original on 2006-02-03. Retrieved 2006-05-08. {{cite web}}: Unknown parameter |coauthors= ignored (|author= suggested) (help)
• Greg H Sherley (1998). "Threatened Weta Recovery Plan" (PDF). Department of Conservation. Retrieved 2007-11-07.
• Wallis, G. P. (2000). "Phylogeographical pattern correlates with Pliocene mountain building in the alpine scree weta (Orthoptera, Anostostomatidae)". Molecular Ecology. 9 (6): 657–666. doi:10.1046/j.1365-294x.2000.00905.x. PMID 10849282. {{cite journal}}: Cite has empty unknown parameter: |month= (help); Unknown parameter |coauthors= ignored (|author= suggested) (help)
• Bleakley, Craig (2006). Design and use of artificial refuges for monitoring adult tree weta, Hemideina crassidens and H. thoracica. Wellington, N.Z.: Science & Technical Pub., Dept. of Conservation. ISBN 9780478140620. {{cite book}}: Unknown parameter |coauthors= ignored (|author= suggested) (help)
• Salmon, J. T. (January 1956). "A Key to the Tree and Ground Wetas of New Zealand". Tuatara. 6 (1).

External links

• Weta at the New Zealand Department of Conservation
• Bug identification - Orthoptera at Landcare Research
• Weta at the Forest and Bird Kiwi Conservation Club
• Wētā in Te Ara - the Encyclopedia of New Zealand
• The Secret Life of Wetas - with insect expert George Gibbs

• Weta