Deinacrida rugosa
Encyclopedia
Deinacrida rugosa, commonly called the Cook Strait giant weta, is a species of insect
in the family
Anostostomatidae
. The scientific name "Deinacrida" means "terrible grasshopper" and "rugosa" means "wrinkled". It is endemic to New Zealand
.
, Maud
, Matiu/Somes and Mana
. 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. It is found in open grassland, shrubland and forest margins.
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. 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. 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.
. 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.
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. 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.
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.
Insect
Insects are a class of living creatures within the arthropods that have a chitinous exoskeleton, a three-part body , three pairs of jointed legs, compound eyes, and two antennae...
in the family
Family (biology)
In biological classification, family is* a taxonomic rank. Other well-known ranks are life, domain, kingdom, phylum, class, order, genus, and species, with family fitting between order and genus. As for the other well-known ranks, there is the option of an immediately lower rank, indicated by the...
Anostostomatidae
Anostostomatidae
Anostostomatidae is a family in the order Orthoptera. It is sometimes referred to as Mimnermidae or Henicidae in some taxonomies, and common names include King crickets in South Africa, and wetas in New Zealand. They are believed to be most closely related to the Jerusalem crickets of North America...
. The scientific name "Deinacrida" means "terrible grasshopper" and "rugosa" means "wrinkled". It is endemic to New Zealand
New Zealand
New Zealand is an island country in the south-western Pacific Ocean comprising two main landmasses and numerous smaller islands. The country is situated some east of Australia across the Tasman Sea, and roughly south of the Pacific island nations of New Caledonia, Fiji, and Tonga...
.
Description
The Cook Strait giant weta is one of the largest insects in the world, reaching up to 7 centimetres (2.8 in) 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.Distribution and habitat
The Cook Strait giant weta is found only in New Zealand, on the islands of the North, South and Middle Trio, StephensStephens Island, New Zealand
Stephens Island is at the northern most tip of the Marlborough Sounds in the South Island of New Zealand. It lies two kilometres to the northeast of Cape Stephens, the northernmost point of D'Urville Island. The Māori call the island Takapourewa but Stephens Island is the commonly used name...
, Maud
Maud Island
Maud Island, originally called Te Hoiere in the Māori language, is the second-largest island in the Marlborough Sounds on the northern tip of the South Island of New Zealand, with a total area of .-Fauna:...
, Matiu/Somes and Mana
Mana Island, New Zealand
Mana Island is the smaller of two islands that lie off the southwest coast of the North Island of New Zealand . The island’s name is an abbreviation of Te Mana o Kupe, "the mana of Kupe"....
. 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. It is found in open grassland, shrubland and forest margins.
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).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. 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. 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.
Threats
A number of animals prey on the Cook Strait giant weta, including birds and reptiles such as the tuataraTuatara
The tuatara is a reptile endemic to New Zealand which, though it resembles most lizards, is actually part of a distinct lineage, order Sphenodontia. The two species of tuatara are the only surviving members of its order, which flourished around 200 million years ago. Their most recent common...
. 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.
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
Black Rat
The black rat is a common long-tailed rodent of the genus Rattus in the subfamily Murinae . The species originated in tropical Asia and spread through the Near East in Roman times before reaching Europe by the 1st century and spreading with Europeans across the world.-Taxonomy:The black rat was...
(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. 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.
Conservation
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 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.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.
Sources
- World Conservation Monitoring Centre 1996. Deinacrida rugosa. 2006 IUCN Red List of Threatened Species. Downloaded on 9 August 2007.