WÃÂtÃÂ (also spelled weta in English) is the common name for a group of about 100 insect species in the families Anostostomatidae and Rhaphidophoridae endemic to New Zealand. They are giant flightless crickets, and some are among the heaviest insects in the world. Generally nocturnal, most small species are carnivores and scavengers while the larger species are herbivorous. Although some endemic birds (and tuatara) likely prey on them, wÃÂtÃÂ are disproportionately preyed upon by introduced mammals, and some species are now critically endangered.
WÃÂtÃÂ is a loanword, from the MÃÂori-language word , which refers to this whole group of large insects; some types of wÃÂtÃÂ have a specific MÃÂori name. In New Zealand English, it is spelled either "weta" or "wÃÂtÃÂ". The form with macrons is increasingly common in formal writing, as the MÃÂori word (without macrons) instead means "excrement". Words of MÃÂori origin in New Zealand English are both singular and plural.
Many wÃÂtÃÂ are large by insect standards and some species are among the largest and heaviest in the world. 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, wÃÂtÃÂ 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 but closely related to winged species in Australia. Different species have different diets. Most wÃÂtÃÂ are predators or omnivores preying on other invertebrates, but the tree and giant wÃÂtÃÂ eat mostly lichens, leaves, flowers, seed-heads, and fruit.
Male giant wÃÂtÃÂ (Deinacrida spp.) are smaller than females and they show scramble competition for mates. Tree wÃÂtÃÂ (Hemideina spp.) males have larger heads than females and a polygynandrous mating system with harem formation and male-male competition for mates. Ground wÃÂtÃÂ (Hemiandrus spp.) males provide nuptial food gifts when mating and females of some species provide maternal care. WÃÂtÃÂ eggs are laid in soil over the autumn and winter months and hatch the following spring. A wÃÂtÃÂ 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.
WÃÂtÃÂ can bite with powerful mandibles. Tree wÃÂtÃÂ bites are painful but not particularly common. Tree wÃÂtÃÂ lift their hind legs in a defence displays to look large and spiky, but they tend to retreat if given the chance. Tree wÃÂtÃÂ raise their hind legs into the air in warning to foes, and then bring them down to stridulate. Pegs or ridges on the side of their abdomen are struck by a patch of fine pegs at the inner surface of their hind legs (femur) and this action makes a distinctive sound. These actions are also used in defence of a gallery by competing males. The female wÃÂtÃÂ looks as if she has a stinger, but it is an ovipositor, which enables her to lay eggs inside rotting or mossy 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.
Fossilised orthopterans have been found in Russia, China, South Africa, Australia, and New Zealand, but the relationships are open to different interpretations by scientists. Most wÃÂtÃÂ of both families are found in the Southern Hemisphere. WÃÂtÃÂ were probably present in ancient Gondwana before Zealandia separated from it. Rhaphidophoridae dispersed over sea to colonise the Chatham Islands (RÃÂkohu), the Auckland (Motu Maha), Snares (Tini Heke), Bounty (Moutere Hauiri) and Campbell (Motu Ihupuku) Islands. The present species might have resulted from a recent radiation, which conflicts with those earlier ideas about dispersal of wÃÂtÃÂ forebears around the Southern Hemisphere (Wallis et al. 2000).
Giant, tree, ground, and tusked wÃÂtÃÂ are all members of the family Anostostomatidae (formerly in the Stenopelmatidae, but recently separated). Cave wÃÂtÃÂ are better referred to as tokoriro, since they are members of the family Rhaphidophoridae, called cave crickets or camel crickets elsewhere, in a different ensiferan superfamily. In New Zealand there were as of 2014 19 genera of tokoriri, and their taxonomy is under review. Seven new species of South Island cave wÃÂtÃÂ were named and described in 2019, including Pleioplectron rodmorrisi.
The 11 species of giant wÃÂtà(Deinacrida spp.) are endemic to New Zealand and legally protected. Giant wÃÂtà(wÃÂtàpunga in MÃÂori) are large by insect standards. They are heavy herbivorous Orthoptera with a body length of up to , excluding their long legs and antennae, and weigh about 20âÂÂ30 g. A captive giant wÃÂtà(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 wÃÂtàis the Little Barrier Island wÃÂtÃÂ, also known as the wÃÂtÃÂpunga. Giant wÃÂtàtend to be less social and more passive than tree wÃÂtà(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 wÃÂtàD. connectens), and are sometimes considered examples of island gigantism.
Tree wÃÂtÃÂ (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 or where rot has set in after a twig has broken off. The hole, called a gallery, is maintained by the wÃÂtÃÂ and any growth of the bark surrounding the opening is chewed away. They readily occupy a preformed gallery in a piece of wood (a "wÃÂtÃÂ 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. Tree wÃÂtÃÂ are nocturnal. Their diet consists of plants and small insects. The males have much larger jaws than the females, though both sexes will stridulate and bite when threatened.
The seven species of tree wÃÂtà(pà «tangatanga in MÃÂori) are:
The North Island species each have a distinctive set of chromosomes (karyotype). 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 wÃÂtÃÂ 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 wÃÂtÃÂ look similar to ground wÃÂtÃÂ. Tusked wÃÂtÃÂ are mainly carnivorous, eating worms and insects. There are three known species in two different subfamilies: the Northland tusked wÃÂtÃÂ Anisoura nicobarica (originally described as a ground wÃÂtÃÂ, Hemiandrus monstrosus), in the subfamily Deinacridinae; the Mercury Islands tusked wÃÂtÃÂ Motuweta isolata; and the most recently discovered, the Raukumara tusked wÃÂtÃÂ Motuweta riparia. Motuweta is in the same subfamily as ground wÃÂtÃÂ, Anostostomatinae.
The Northland tusked wÃÂtÃÂ lives in tree holes, similar to tree wÃÂtÃÂ. The Mercury Islands or Middle Island tusked wÃÂtÃÂ was discovered in 1970. It is a ground-dwelling wÃÂtÃÂ, 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 wÃÂtÃÂ 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.
Ground wÃÂtàare classified in to the two genera Hemiandrus and Anderus. The species in these two genera are each more closely related to winged Australian species than they are to each other. About 30 species of ground wÃÂtàoccur in New Zealand, and several similar (undescribed) species are found in Australia. They are also very like the Californian CnemotettixâÂÂa similarity perhaps due to their very similar habits and habitat. 19 Hemiandrus species have been described from New Zealand and other distinct populations require further study. They hide in burrows in the ground during the day, and those that live in open ground (e.g., H. focalis, H. maia) conceal their exit holes with a specially made perforated door. During the night, ground wÃÂtàhunt invertebrate prey and eat fruit. Most female ground wÃÂtàhave long ovipositors (e.g. H. maculifrons), but some have short ovipositors and maternal care (e.g. H. maia, H. pallitarsis).
The 60 species of cave wÃÂtÃÂ or tokoriro are only very distant relatives of the other types of wÃÂtÃÂ, being classified in several genera of subfamily Macropathinae in family Rhaphidophoridae.
They 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 (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). 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.
Although wÃÂtÃÂ 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 over 100 species at risk. Programmes to prevent extinctions have been implemented since the 1970s.
Some especially endangered species are tracked by radio beacons.
New Zealanders Peter Jackson, Richard Taylor, and Jamie Selkirk founded visual effects company Weta Digital (now known as WÃÂtÃÂ FX), naming it after the insect. One of Jackson's films, King Kong, has among the Skull Island fauna oversized versions of the giant wÃÂtÃÂs, referred to with the scientific name "Deinacrida rex" or "WÃÂtÃÂ-rex".