Deinacrida rugosa, commonly called the Cook Strait giant weta or Stephens Island weta,[1] is a species of insect in the familyAnostostomatidae. The scientific name Deinacrida means "terrible grasshopper" and rugosa means "wrinkled". It is endemic to New Zealand.
The Cook Strait giant weta is one of the largest insects in the world, reaching up to 7 centimetres (2.8in) long.[3] The brownish-yellow body is bulky and heavily armoured, with the upper surface covered by a series of thickened, overlapping plates, which have black markings. Relative to the size of the head, the jaws are large, and the elongated hind legs have five or six large spines, and can be raised above the head in defence. The female is significantly larger than the male, and both sexes lack wings.[4]
Distribution and habitat
The Cook Strait giant weta is found only in New Zealand, on the islands of the North, South and Middle Trio, Stephens, Maud, Matiu/Somes and Mana.[4] In 2007, this species was reintroduced to mainland New Zealand, where it had been extinct for over 100 years, and is now found in Zealandia Wildlife Sanctuary in the North Island.[5] It is found in open grassland, shrubland and forest margins.[4]
Biology
The Cook Strait giant weta is nocturnal and feeds on the aerial parts of plants. During the day it conceals itself amongst grass in a temporary refuge that it makes in the soil surface, or under dead leaves, bark or stones. It emerges just after dusk, foraging on the ground or on low-growing bushes and shrubs, where it particularly favours tauhinu flowers (Cassinia leptophylla).[4]
Owing to its solitary and nomadic lifestyle, the Cook Strait giant weta's reproduction relies upon the male locating a receptive female. This search is facilitated by the strong scent produced by the weta's body and by its faecal pellets, and can involve the male travelling over 250 metres in a single night.[6] Once located, the male places a leg over the female's body and maintains contact until a daytime refuge is found. Here, mating occurs throughout the day and, if the weather is cool and wet, possibly throughout the night as well.[7] The female subsequently lays around 200 eggs in the soil and dies. The eggs develop for a few months and hatch in the spring, with the juvenile wetas emerging fully developed. It takes most of the Cook Strait giant weta's two-year lifespan to reach the full adult size, with growth taking place in a series of about nine moults over a 12- to 18-month period.[5]
Threats
A number of animals prey on the Cook Strait giant weta, including birds and reptiles such as the tuatara. As a defence against predators the Cook Strait giant weta will raise its spiked legs over its head and wave them up and down while making a hissing sound by rapidly rubbing together the overlapping plates on its upper body.[8]
Historically, the Cook Strait giant weta was found on mainland New Zealand as well as many off-shore islands, but the introduction of mammalian predators such as the black rat (Rattus rattus), and the clearance of much of its habitat, led to the contraction of its range to just a few small, "rat-free" islands in the Cook Strait.[9] A combination of its ground-dwelling lifestyle, large size, and strong scent make it particularly vulnerable to predation, and therefore, accidental introductions of mammalian predators to the offshore islands could be catastrophic for its survival.[6]
Conservation
Deinacrida rugosa specimen
Introductions of the Cook Strait giant weta to Mana Island in 1976, Matiu / Somes Island in 1996, and, most recently, Zealandia Wildlife Sanctuary in the North Island in 2007 have helped to greatly expand this vulnerable species' range. In addition, on Mana Island, the removal of cattle and eradication of mice has dramatically increased Cook Strait giant weta abundance. With the success of these introductions, the New Zealand Department of Conservation plans to continue to introduce the Cook Strait giant weta to new island habitats, while ensuring that its existing island habitats remain protected against the threat of predator invasion.[9]
The Matiu-Somes Island transfer was undertaken in 1996 with two separate translocations taking place.[10] In total 62 individual weta were released and were sourced from Mana Island.[10] Surveys of the Cook Strait giant weta were undertaken on Matiu-Somes Island in 2013 and 2015.[10]
The species has been introduced to Zealandia Wildlife Sanctuary. By using a specially designed fence to exclude mammalian predators, the sanctuary hopes to re-establish an environment similar to that which existed on New Zealand before the arrival of humans, where species such as the Cook Strait giant weta can thrive once more.[5]
The Cook Strait giant weta was assessed by the Department of Conservation as "At Risk: Relict", with a stable but small population.[2]
1 2 Trewick, Steven A.; Johns, P. M.; Hitchmough, Rod A.; Rolfe, Jeremy; Stringer, Ian (2016). Conservation status of New Zealand Orthoptera, 2014. New Zealand Threat Classification Series. Wellington, N.Z: Department of Conservation.
↑ Field, L.H. (2001) The Biology of Wetas, King Crickets and Their Allies. CABI Publishing, Wallingford.
1 2 Sherley, G.H. (1998). "Threatened Weta Recovery Plan"(PDF). New Zealand Threatened Species Recovery Plans. Biodiversity Recovery Unit, Department of Conservation, Wellington. 25.
Anostostomatidae is a family of insects in the order Orthoptera, widely distributed in the southern hemisphere. It is named Mimnermidae or Henicidae in some taxonomies, and common names include king crickets in Australia and South Africa, and wētā in New Zealand. Prominent members include the Parktown prawn of South Africa, and the giant wētā of New Zealand. The distribution of this family reflects a common ancestry before the fragmenting of Gondwana.
Giant wētā are several species of wētā in the genus Deinacrida of the family Anostostomatidae. Giant wētā are endemic to New Zealand and all but one species are protected by law because they are considered at risk of extinction.
The Northland tusked wētā, Anisoura nicobarica, is a rare monotypic wētā of the family Anostostomatidae, endemic to the northern half of Northland in New Zealand, and originally described in 1932. The type specimen was wrongly labelled as coming from the Nicobar Islands, so the species was named Anisoura nicobarica. It was erroneously described again in 1950 by a different author, who placed it in the ground wētā genus Hemiandrus.
Deinacrida fallai or the Poor Knights giant wētā is a species of insect in the family Anostostomatidae. It is endemic to the Poor Knights Islands off northern New Zealand. D. fallai are commonly called giant wētā due to their large size. They are one of the largest insects in the world, with a body length measuring up to 73 mm. Their size is an example of island gigantism. They are classified as vulnerable by the IUCN due to their restricted distribution.
Deinacrida heteracantha, also known as the Little Barrier giant wētā or wētāpunga, is a wētā in the order Orthoptera and family Anostostomatidae. It is endemic to New Zealand, where it survived only on Little Barrier Island, although it has been translocated to some other predator-free island conservation areas. This very large flightless wētā mainly feeds at night, but is also active during the day, when it can be found above ground in vegetation. It has been classified as vulnerable by the IUCN due to ongoing population declines and restricted distribution.
Deinacrida parva is a species of insect in the family Anostostomatidae, the king crickets and weta. It is known commonly as the Kaikoura wētā or Kaikoura giant wētā. It was first described in 1894 from a male individual then rediscovered in 1966 by Dr J.C. Watt at Lake Sedgemore in Upper Wairau. It is endemic to New Zealand, where it can be found in the northern half of the South Island.
Deinacrida connectens, often referred to as the alpine scree wētā, is one of New Zealand's largest alpine invertebrates and is a member of the Anostostomatidae family. Deinacrida connectens is a flightless nocturnal insect that lives under rocks at high elevation. Mountain populations vary in colour. This species is the most widespread of the eleven species of giant wētā (Deinacrida).
Deinacrida carinata, also known as the Herekopare wētā or Foveaux wētā is one of the smallest of the 11 species of giant wētā that belong to the genus Deinacrida, and is a member of the family Anostostomatidae. It is endemic to New Zealand and is currently restricted to a few offshore predator free islands: Herekopare Island, Kundy Island, Tihaka/Pig Island and Whenua Hou/Codfish Island. D.carinata is a protected species and is nationally endangered.
Deinacrida tibiospina, also known as the Mt Arthur giant wētā or the Nelson alpine giant wētā, is a species of wētā in the family Anostostomatidae. It is endemic to the South Island of New Zealand. The wētā is only found in some alpine zones of Kahurangi National Park. Compared with natural densities of other wētā, D. tibiospina is fairly rare. Little conservation effort has been made for this species because, despite its elusiveness, populations on the mainland have been maintained without human intervention.
Deinacrida elegans is a species of wētā in family Anostostomatidae. It is endemic to New Zealand.
Deinacrida mahoenui, the Mahoenui giant wētā, is a flightless insect in the giant wētā family Anostostomatidae. It is endemic to the area of Mahoenui, New Zealand, and the world population for some time was restricted to a single patch of introduced gorse on farmland.
Deinacrida talpa, the giant mole weta, is a species of insect in the family Anostostomatidae. It is endemic to New Zealand. Although the species is similar to closely related species, its key distinguishing factor is their ability to live in burrows dug by the weta. The Department of Conservation assessed its status as "At Risk: Naturally Uncommon".
The Mercury Islands tusked wētā, Motuweta isolata, also known as the Middle Island tusked wētā, is a large flightless insect in the family Anostostomatidae, discovered in 1970 living on a single small island in New Zealand. Distinguished by the enormous tusks with which males fight, it was saved from extinction by a captive breeding programme and translocation: the entire world population is descended from a male and two females captured and bred in captivity in 1998, just before the species went extinct in the wild. Motuweta isolata is the largest of the three tusked wētā species, and the most endangered wētā, ranked Nationally Critical by the Department of Conservation.
Hemideina ricta, known as the Banks Peninsula tree wētā, is an insect that is endemic to New Zealand.
Hemideina thoracica, commonly known as the Auckland tree wētā or tokoriro is a cricket-like insect. It is endemic to New Zealand and is found over most of the North Island, except for the Wellington region and regions 900 metres above sea level. This species is an arboreal, herbivorous generalist however, it is also thought to be polyphagous and is found in all wooded habitats, including forest, scrub and suburban gardens.
Corinne Hannah Watts is a New Zealand entomologist and ecologist. Specimens collected by Watts are held at Museum of New Zealand Te Papa Tongarewa.
Hemiandrus bilobatus, the wine wētā, is a species of ground weta endemic to New Zealand. Being a ground weta, they are often found in burrows in the ground during the daytime. The species is found in Wellington, on Mana Island and northern South Island and is classified as "Not Threatened". This species of weta is unusual for an insect in that the female shows maternal care. She lays about 50 eggs in the same burrow she uses during the day and looks after her eggs until they hatch.
Hemiandrus maculifrons is a species of ground wētā endemic to New Zealand. They are nocturnal, carnivorous, and flightless orthopterans belonging to the family Anostostomatidae. Being a nocturnal species, individuals remain in tunnels in the ground during the day and emerge from their burrows after sunset to forage and hunt for small invertebrates. H. maculifrons is one of the smallest New Zealand weta species, averaging 15 mm in length and weighing 1–3 g. Unlike the tree weta and tusked weta, where sexual dimorphism is found in the form of male weaponry, ground weta only exhibit sexual size dimorphism: the females are larger than the males.
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Hemiandrus furoviarius, commonly known as the Tekapo ground wētā, is a wētā of the family Anostostomatidae. They are a small, flightless, and nocturnal orthopteran endemic to the Mackenzie Basin of New Zealand's South Island.
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