Deinacrida parva

Deinacrida parva
Conservation status
Data Deficient  (IUCN 2.3)[1]
Scientific classification
Domain:	Eukaryota
Kingdom:	Animalia
Phylum:	Arthropoda
Class:	Insecta
Order:	Orthoptera
Suborder:	Ensifera
Family:	Anostostomatidae
Genus:	Deinacrida
Species:	D. parva
Binomial name
Deinacrida parva Buller, 1895

Deinacrida parva is a species of insect in the family Anostostomatidae, the king crickets and weta. It is known commonly as the Kaikoura wētā^[1] or Kaikoura giant wētā.^[2] It was first described in 1894 from a male individual^[3] then rediscovered in 1966 by Dr J.C. Watt at Lake Sedgemore in Upper Wairau.^[4] It is endemic to New Zealand, where it can be found in the northern half of the South Island.^[2]

This is a small to medium-sized robust wētā.^[5] It is easily confused with Deinacrida rugosa.^[2][6][7] Due to the rarity of this weta, there is still much to be learnt.^[8]

Deinacrida parva have a rounded brown body.^[9] The females are larger than the males in this species of wētā, but the males have long legs suggesting scramble competition for mates.^[10][11] The females have a large spike on the end of their body, this spike is called an ovipositor and is used for laying eggs.^[12]

The Kaikoura giant wētā can grow up to around 100mm in size^[12] and weigh up to 14.5 grams.^[13] They have a life span of roughly two years.^[4] This wētā, although very similar in appearance, is smaller in size than D. rugosa and is a brown colour^[10] with darker colouring under the abdomen.^[9] Red or pink coloration can also be present on the border of the thoracic shield.^[2] A major identification of the Kaikoura Wētā is by counting the six spines present on the lower hind leg.^[2]

The taxonomic status of D.parva and D. rugosa were investigated.^[2] These two are species are morphologically similar and phylogenetically sister species.^[14]

Deinacrida parva are found in many different terrestrial environments^[15] but most commonly under large logs on river flats and scrub areas close to the edges of the forests.^[2] Large proportions of individuals are found under Mataī logs.^[8] Their preference for living close to water ways has resulted in the drowning of some individuals, although this might be linked to infection by internal parasites.^[13]

D. parva are found between 150 and 1500m above sea level from South Marlborough to Hanmer Springs.^[2] These weta are considered subalpine specialists.^[16] They are most common surrounding Hapuku and Kowhai river close to Kaikōura (hence the name of these wētā).^[2]

It is suspected they now occupy less than 10% of their former range.^[17]

Deinacrida parva are herbivorous and feed mainly on the leaves of trees and shrubs.^[18] Females of this species have been known to eat carcasses of dead or dying insects for extra protein during breeding season for egg development.^[8]

This weta, like many of the other weta in New Zealand, is nocturnal.^[19]

D. parva are able to produce sounds by rubbing tergite spines and hair sensilla together (located on their abdominal plates).^[5] The sounds are normally produced during contraction of the abdomen and often in time with a defensive leg kick as a warning.^[5] This is called the tergo-tergal mechanism.^[5] The sounds produced are a soft hiss and often fall within ultrasonic frequencies.^[5]

Using hair sensilla for sound production is a rare occurrence in arthropods and a potential explanation for why it has occurred in this species is that it has evolved under predation pressure by the endemic short-tailed bat in New Zealand.^[5] There are no current evidence that the sounds produced are for intraspecific communication but it has not been researched extensively.^[5]

D. parva have been breed in captivity.^[2] But due to wētā being captured at different ages and conditions, breeding pairs were hard to establish.^[4] Young wētā come to sexual maturity successfully in captivity but some fail to lay eggs.^[8] Females lay eggs in the soil with an ovipositor.^[12]

Populations in some parts have declined to a few individuals.^[2] Many of the die-offs have been in the large populations close to Kaikoura.^[2] Even though there has been a die off the population is considered to be stable.^[17]

A major reason for decline is likely due to habitat clearance and predation by pests.^[2] The changes in the natural habitat of D. parva has affected the chances of future survival in many of the smaller recorded populations.^[2] Many of their original habitats have been cleared for pasture.^[4] The die-offs could be associated with the Gordian worm parasite.^[2] But the full impact of the parasite is unknown and still requires further research.^[8] D. parva that become hosts for the Gordian worm parasite have been shown to have lowered reproductive capabilities.^[8]

Further population surveys and full distribution research needs to be conducted for further information.^[8] Although that has been difficult due to low population numbers, thick vegetation and uneven grounds.^[8] Searching for these weta in the fallen logs (where they are most likely to be found) also damages and degrades the logs quicker and leaves less available habitats for them.^[4] It has been proposed that they should be bred and then released on predator-free islands.^[8] Mainland habitat management has also been suggested as a conservation plan.^[4]

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