T.E.R:R.A.I.N - Taranaki Educational Resource: Research, Analysis and Information Network


Weta (Little Barrier Island giant weta) Deinacrida heteracantha

Kingdom: Animalia
Phylum: Arthropoda
Class: Insecta
Order: Orthoptera
Family: Anostostomatidae
Genus: Deinacrida
Species: D. heteracantha
Binomial name: Deinacrida heteracantha
Common name: Little Barrier Island giant weta, Wetapunga

Deinacrida heteracantha is a large cricket that is an arboreal forest dweller on Little Barrier Island (3083ha in size) which lies off the coast of New Zealand. They are also on several smaller predator-free island conservation areas. It has been classified as vulnerable by the IUCN due to ongoing population declines and restricted distribution.

They once occupied forests in northern New Zealand but have since disappeared due to predation and habitat loss. The main predators of D. heteracantha are the rat (Rattus exulans), North Island saddleback (Philesturnus rufusater). Other predators include Tuatara, Geckos and the North Island Brown Kiwi (Apteryx mantelli) during the night, Kingfisher (Todiramphus sanctus) and Eudynamys taitensis (long-tailed cuckoo) by day.

On Little Barrier Island their habitat range is in the lower slopes of second-growth forests of Silverfern (Cyathea dealbata), Nikau palm (Rhopalostylis sapida), Mahoe (Melicytus ramiflorus), Kohekohe (Dysoxylum spectabile) and Pohutukawa (Metrosideros excelsa). They also inhabit the island’s mid-level tall Kauri (Agathis australis) forest.

D. heteracantha is a large species of cricket with the average weight between 9-35 g. and with an average body length of around 75 mm. In 2011 one was weighed at 71 g. They live a solitary, nomadic lifestyle periodically moving to a new location.
It is a sexually dimorphic species with the females being much larger than the males. They have a broad body and a round head, along with short mandibles. This species is mainly herbivorous and feeds on forest foliage. It mainly feeds at night, but is also active during the day, when it can be found above ground in vegetation under loose bark or in the cavities in tree trunks.

The life cycle of D. heteracantha are not tied to the seasons. They can live for up to two years. Eggs are laid in the summer months from October to December. The eggs will then hatch in March and April of the following year. D. heteracantha mate most months of the year except for the winter months from June–August. Copulation will start in the morning and continue throughout the day. During copulation the spermatophore from the male is inserted into the female’s subgenital plate. Females lay their eggs at night into moist soil. Each egg is laid singly or in groups of five in area that is about 15cm2 and about 2–3 cm deep. Females only produce an indefinite amount of eggs. Females lay eggs for the rest of their lives, but only a limited number of them are fertilized during each copulation. The eggs incubate on average for 125 days and only 36% of the eggs survive to hatch.
After the eggs hatch there are ten instars that they go through until death. In females the ovipositor becomes visible at the third instar. At the sixth instar the difference between male and female sexes becomes obvious. Each instar lasts on average between five to six weeks. D. heteracantha has an extra instar compared to other species in its genus, this extra instar is what makes the nymphal period longer and their overall body size larger.

A large female.