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| binomial_authority = Buller, 1871
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'''''Deinacrida rugosa''''' or '''Cook Strait giant weta''' is a species of [[insect]] in family [[Stenopelmatidae]]. It is [[Endemism|endemic]] to [[New Zealand]].
'''''Deinacrida rugosa''''' or '''Cook Strait giant weta''' is a species of [[insect]] in the [[Family (biology)|family]] [[Stenopelmatidae]]. The scientific name ''"Deinacrida"'' means "terrible grasshopper" and "rugosa" means "wrinkled". It is [[Endemism|endemic]] to [[New Zealand]].

==Description==
The Cook Strait giant weta is one of the largest insects in the world, reaching up to seven centimetres long. 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.<ref name=NZDC>[http://www.doc.govt.nz/upload/documents/conservation/native-animals/invertebrates/020-weta-ii.pdf ''Deinacrida rugosa''] New Zealand Department of Conservation (November, 2008)</ref>

==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.<ref name=NZDC/> In 2007, this species was reintroduced to mainland New Zealand, where it had been extinct for over 100 years, and is now found in Karori Wildlife Sanctuary on North Island.<ref name=KWS>[http://www.sanctuary.org.nz/ Karori Wildlife Sanctuary]</ref> It is found in open grassland, shrubland and forest margins.<ref name=NZDC/>

==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]]'').<ref name=NZDC/>

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.<ref>Gibbs, G.W. (1998) Why are some weta (Orthoptera: Stenopelmatidae) vulnerable yet others are common?. Journal of Insect Conservation, 2: 161 - 166.</ref> 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.<ref>Kelly, C.D., Bussière, L.F. and Gwynne, D.T. (2008) Sexual Selection for Male Mobility in a Giant Insect with Female-Biased Size Dimorphism. The American Naturalist, 172: 417 - 422.</ref> 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.<ref name=KWS/>

== 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.<ref>Field, L.H. (2001) ''The Biology of Wetas, King Crickets and Their Allies.'' CABI Publishing, Wallingford.</ref>

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.<ref name="Sherley" /> 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.<ref name="Gibbs">{{cite journal|last=Gibbs|first=G.W.|year=1998|title=Why are some weta (''Orthoptera: Stenopelmatidae'') vulnerable yet others are common?|journal=Journal of Insect Conservation|volume=2|pages=161–166}}</ref>

== Conservation ==

Introductions of the Cook Strait giant weta to Mana Island in 1976, Matiu-Somes Island in 1996, and, most recently, Karori Wildlife Sanctuary on 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 the Cook Strait giant weta’s 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.<ref name="Sherley">{{cite journal|last=Sherley|first=G.H.|year=1998|title=Threatened Weta Recovery Plan|journal=New Zealand Threatened Species Recovery Plans|publisher=Biodiversity Recovery Unit, Department of Conservation, Wellington|volume=25|url=http://www.doc.govt.nz/upload/documents/science-and-technical/tsrp25.pdf}}</ref>

The species has been introduced to Karori 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.<ref name="KWS">{{cite web|url=http://www.sanctuary.org.nz/|title=Karori Wildlife Sanctuary|date=2008-11|accessdate=2008-11}}</ref>


==Sources==
==Sources==
{{reflist}}
* {{ARKive attribute}}
* World Conservation Monitoring Centre 1996. [http://www.iucnredlist.org/search/details.php/6306/all ''Deinacrida rugosa'']. [http://www.iucnredlist.org 2006 IUCN Red List of Threatened Species. ] Downloaded on 9 August 2007.
* World Conservation Monitoring Centre 1996. [http://www.iucnredlist.org/search/details.php/6306/all ''Deinacrida rugosa'']. [http://www.iucnredlist.org 2006 IUCN Red List of Threatened Species. ] Downloaded on 9 August 2007.


==External links==
==External links==
* {{ARKive|cook-strait-giant-weta|deinacrida-rugosa}}
* {{commonscat-inline|Deinacrida rugosa}}
* {{commonscat-inline|Deinacrida rugosa}}



Revision as of 15:00, 23 August 2011

Cook Strait Giant weta
Cook Strait Giant weta found at Matiu/Somes_Island.

Deinacrida rugosa
Scientific classification
Kingdom:
Phylum:
Class:
Order:
Family:
Genus:
Species:
D. rugosa
Binomial name
Deinacrida rugosa
Buller, 1871

Deinacrida rugosa or Cook Strait giant weta is a species of insect in the family Stenopelmatidae. The scientific name "Deinacrida" means "terrible grasshopper" and "rugosa" means "wrinkled". It is endemic to New Zealand.

Description

The Cook Strait giant weta is one of the largest insects in the world, reaching up to seven centimetres long. 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.[1]

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.[1] In 2007, this species was reintroduced to mainland New Zealand, where it had been extinct for over 100 years, and is now found in Karori Wildlife Sanctuary on North Island.[2] It is found in open grassland, shrubland and forest margins.[1]

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).[1]

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.[3] 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.[4] 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.[2]

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.[5]

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.[6] 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.[7]

Conservation

Introductions of the Cook Strait giant weta to Mana Island in 1976, Matiu-Somes Island in 1996, and, most recently, Karori Wildlife Sanctuary on 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 the Cook Strait giant weta’s 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.[6]

The species has been introduced to Karori 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.[2]

Sources

  1. ^ a b c d Deinacrida rugosa New Zealand Department of Conservation (November, 2008)
  2. ^ a b c Karori Wildlife Sanctuary Cite error: The named reference "KWS" was defined multiple times with different content (see the help page).
  3. ^ Gibbs, G.W. (1998) Why are some weta (Orthoptera: Stenopelmatidae) vulnerable yet others are common?. Journal of Insect Conservation, 2: 161 - 166.
  4. ^ Kelly, C.D., Bussière, L.F. and Gwynne, D.T. (2008) Sexual Selection for Male Mobility in a Giant Insect with Female-Biased Size Dimorphism. The American Naturalist, 172: 417 - 422.
  5. ^ Field, L.H. (2001) The Biology of Wetas, King Crickets and Their Allies. CABI Publishing, Wallingford.
  6. ^ a b Sherley, G.H. (1998). "Threatened Weta Recovery Plan" (PDF). New Zealand Threatened Species Recovery Plans. 25. Biodiversity Recovery Unit, Department of Conservation, Wellington.
  7. ^ Gibbs, G.W. (1998). "Why are some weta (Orthoptera: Stenopelmatidae) vulnerable yet others are common?". Journal of Insect Conservation. 2: 161–166.

External links