The Northland tusked wētā, ''Anisoura nicobarica'', is a rare

monotypic In biology, a monotypic taxon is a taxonomic group (taxon) that contains only one immediately subordinate taxon. A monotypic species is one that does not include subspecies or smaller, infraspecific taxa. In the case of genera, the term "unisp ...

wētā Wētā (also spelled weta in English) is the common name for a group of about 100 insect species in the families Anostostomatidae and Rhaphidophoridae endemism, endemic to New Zealand. They are giant wingless insect, flightless cricket (insect ...

of the

family Family (from ) is a Social group, group of people related either by consanguinity (by recognized birth) or Affinity (law), affinity (by marriage or other relationship). It forms the basis for social order. Ideally, families offer predictabili ...

Anostostomatidae 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, an ...

endemic Endemism is the state of a species being found only in a single defined geographic location, such as an island, state, nation, country or other defined zone; organisms that are indigenous to a place are not endemic to it if they are also foun ...

to the northern half of Northland in

New Zealand New Zealand () is an island country in the southwestern Pacific Ocean. It consists of two main landmasses—the North Island () and the South Island ()—and List of islands of New Zealand, over 600 smaller islands. It is the List of isla ...

, and originally described in 1932. The type specimen was wrongly labelled as coming from the

Nicobar Islands The Nicobar Islands are an archipelago, archipelagic island chain in the eastern Indian Ocean. They are located in Southeast Asia, northwest of Aceh on Sumatra, and separated from Thailand to the east by the Andaman Sea. Located southeast of t ...

, 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'' (as ''Hemiandrus monstrosus)''.

Description

Tusked

are distinctive because of the long curved "tusks" adult males have projecting forward from their jaws. The tusks are not used for biting but are used to push an opponent. Among the three species of tusked

, the Northland tusked wētā, ''Anisoura nicobarica,'' is the smallest measuring up to 21mm in body length. The Middle Island tusked wētā, ''Motuweta isolata,'' being the biggest measuring up to 70 mm in body length and the Raukumara tusked wētā, ''Motuweta riparia,'' is 30–40 mm long. The Northland tusked wētā is reddish brown and their hind tibia contains small spines. The tusks are devoid of stridulatory ridges, which are a feature of both '' M. isolata'' and ''A. nicobarica''''.'' Unlike ground wētā (''Hemiandrus'' sp.), tusked wētā have ears on their front legs (fore-tibia).

Habitat

The Northland tusked wētā is

arboreal Arboreal locomotion is the locomotion of animals in trees. In habitats in which trees are present, animals have evolved to move in them. Some animals may scale trees only occasionally (scansorial), but others are exclusively arboreal. The hab ...

so needs native forest and scrub. Similar to the tree wētā, ''

Hemideina thoracica ''Hemideina thoracica'', commonly known as the Auckland tree wētā or tokoriro is a cricket-like insect (within the family Anostostomatidae). It is endemic to New Zealand and is found over most of the North Island, except for the Wellington re ...

,'' both species occupy holes (galleries) in manuka and other trees and shrubs during the day. Unlike tree wētā, the tusked wētā makes a seal to close the hole entrance. Because the Northland tusked wētā hides in hollow branches and trunks of manuka it is often found associated with firewood.

Distribution and abundance

''Anisoura nicobarica'' are

to the Far North of

. In 1948 a specimen was found at Orokawa Bay in the

Bay of Islands The Bay of Islands is an area on the east coast of the Far North District of the North Island of New Zealand. It is one of the most popular fishing, sailing and tourist destinations in the country, and has been renowned internationally for ...

. Most subsequent sightings have come from the

Hokianga The Hokianga is an area surrounding the Hokianga Harbour, also known as the Hokianga River, a long Estuary, estuarine drowned valley on the west coast in the north of the North Island of New Zealand. The original name, still used by local Mā ...

region. Most sightings involve only a single individual, making their abundance hard to determine. Northland tusked wētā are nocturnal and during the day they hide in tree holes and cover the entrance, making them hard to find.

Diet

Like other tusked wētā species, the Northland tusked wēta prefers feeding on an animal diet consisting of live and dead insects and spiders.

Behaviour

Anisoura nicobarica male under mandibles

''Anisoura nicobarica'' lives in tree holes (galleries), while the other two species of tusked wētā are ground burrowers, and all three face outward while occupying the retreat. As a defence tactic the tusked wētā orients itself to face the opening of its gallery with its jaws agape.Messenger, G. (1992). A further record and notes on the Hokianga Tusked Weta. ''WETA.'' 15(2). 33-35 They also mix their saliva with wood scrapings to seal the entrance of their gallery making the aperture almost invisible which is especially important during their moult. A captive ''A. nicobarica'' has been recorded creating a burrow in soil and roofing it with debris which suggests they can be flexible over their selection of refuges.Bellingham, M. (1991) Field observations of two species of tusked weta. The Weta (New Zealand Entomological Society) 14, 30–32. When any of the tusked wētā are provoked further they display " mandible gape", "raise foreleg" and "raise head" which closely resemble a suit of components displayed by '' Hemideina'' species. According to Bellingham, M. (1991) during a field observation stated "when disturbed, they raised their tusks slightly, rasping them together. The body was curved sideways with the front and head elevated. The hind legs were not raised. The weta also made short lunges forward attempting to use its tusks as pincers. When disturbed further, by blowing or tapping lightly on its head, the weta jumped away haphazardly".

Conservation status

Under the

New Zealand Threat Classification System The New Zealand Threat Classification System is used by the Department of Conservation to assess conservation priorities of species in New Zealand. The system was developed because the IUCN Red List, a similar conservation status system, had s ...

, this species is listed as "Declining" with the qualifiers of "Biologically Sparse", "Data Poor: Size", "Data Poor Trend" and "Population Fragmentation". The decline is due to habitat loss. In earlier reports, it was classified as "Relict".

References

External links

NZ Dept of Conservation

Orthoptera Species
{{Taxonbar, from1=Q7059547, from2=Q14593168 Wētā Anostostomatidae Insects described in 1932