Wētā

Cook Strait giant wētā (Deinacrida rugosa)

The 11 species of giant wētā (Deinacrida spp.) are endemic to New Zealand.[11] Giant wētā (wētā punga in Māori)[2] are large by insect standards. They are heavy herbivorous Orthoptera with a body length of up to 100 mm (3.9 in) excluding their lengthy legs and antennae, and weigh about 20–30 g. A captive giant wētā (Deinacrida heteracantha) filled with eggs reached a record 70 g, making it one of the heaviest documented insects in the world[20] and heavier than a sparrow. The largest species of giant wētā is the Little Barrier Island wētā, also known as the wētāpunga. Giant wētā tend to be less social and more passive than tree wētā (Hemideina spp.). 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 or at high elevation on New Zealand's South Island (e.g. the alpine scree wētā D. connectens), and are sometimes considered examples of island gigantism.

Male Hemideina crassidens (Wellington tree wētā)

Tree wētā (Hemideina) are commonly encountered in suburban settings in New Zealand's North Island. They are up to 40 mm long and most commonly live in holes in trees formed by beetle and moth larvae[21] or where rot has set in after a twig has broken off. The hole, called a gallery, is maintained by the wētā and any growth of the bark surrounding the opening is chewed away. They readily occupy a preformed gallery in a piece of wood (a "wētā motel") and can be kept in a suburban garden as pets. A gallery might house a harem of up to 10 adult females and one male.[8] Tree wētā are nocturnal. Their diet consists of plants and small insects.[6] The males have much larger jaws than the females, though both sexes will stridulate and bite when threatened.[11]

Harem of 5 adult females and one male Wellington tree wētā (Hemideina crassidens)

The seven species of tree wētā (pūtangatanga in Māori)[2] are:

• The Auckland tree wētā Hemideina thoracica can be found throughout the North Island apart from the Wellington-Wairarapa region. Within this range are seven chromosome races.[22]
• The Wellington tree wētā Hemideina crassidens occupies Wellington, the Wairarapa, the northern parts of the South Island, and the West Coast.[23]
• Hemideina trewicki is found in Hawke's Bay.[24]
• H. femorata is found in Marlborough and Canterbury.
• The rare H. ricta species occurs in Banks Peninsula.
• The West Coast bush wētā H. broughi largely overlaps with the Wellington tree wētā in Nelson and the northern portion of the West Coast.
• H. maori, the mountain stone wētā, lives above the tree line in the Southern Alps.

Auckland tree wētā

The North Island species each have a distinctive set of chromosomes (karyotype).[25] 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.[26]

Motuweta isolata, Mercury Islands tusked wētā

Tusked wētā are characterised by long, curved tusks projecting forward from the male's mandibles. The tusks are used in male-to-male combat, not for biting. Female tusked wētā look similar to ground wētā. Tusked wētā are mainly carnivorous, eating worms and insects. There are three known species in two different subfamilies: the Northland tusked wētā Anisoura nicobarica (originally described as a ground wētā, Hemiandrus monstrosus), in the subfamily Deinacridinae; the Mercury Islands tusked wētā Motuweta isolata; and the most recently discovered, the Raukumara tusked wētā Motuweta riparia. Motuweta is in the same subfamily as ground wētā, Anostostomatinae.

The Northland tusked wētā lives in tree holes, similar to tree wētā. The Mercury Islands or Middle Island tusked wētā was discovered in 1970. It is a ground-dwelling wētā, entombing itself in shallow burrows during the day, and is critically endangered: a Department of Conservation breeding programme has established new colonies on other islands in the Mercury group. The Raukumara tusked wētā was discovered in 1996, in the Raukumara Range near the Bay of Plenty. It has the unusual habit of diving into streams and hiding underwater for up to three minutes if threatened.

A male ground wētā, Hemiandrus pallitarsis

Ground wētā are classified in the genus Hemiandrus. About 30 species of ground wētā occur in New Zealand, and several very similar (undescribed) ones are found in Australia.[16] They are also very like the Californian Cnemotettix—a similarity perhaps due to their very similar habits and habitat. 19 Hemiandrus species have been described from New Zealand[27][28] and other distinct populations require further study.[29] They hide in burrows in the ground during the day, and those that live in open ground (e.g., H. focalis, H. maia)[30] conceal their exit holes with a specially made perforated door. During the night, ground wētā hunt invertebrate prey and eat fruit. Most female ground wētā have long ovipositers (e.g. H. maculifrons), but some have short ovipositers and maternal care (e.g. H. maia, H. pallitarsis).

The 60 species of cave wētā or tokoriro[2] are only very distant relatives of the other types of wētā, being classified in several genera of subfamily Macropathinae in family Rhaphidophoridae.

They have extra-long antennae,[31] 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 (such as Talitropsis) 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.

Although some do live in caves, most species (e.g. Talitropsis sedilloti) live in the forest among leaf litter, logs, under bark (e.g. Isoplectron), inside tree holes (e.g. Neonetus sp.) and amongst rocks in the mountains (e.g. Pharmacus).[32][33][34] [35] Cave-dwelling species may be active within the confines of their caves during the daytime, and those individuals close to cave entrances venture outside at night.[34]

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