Weta (Mahoenui Giant Weta) Deinacrida mahoenui
Species: D. mahoenui
Binomial name: Deinacrida mahoenui
Common name: Mahoenui Giant Weta
Deinacrida mahoenui is a species of insect in family Anostostomatidae and it is endemic to New Zealand. This species were discovered in 1962 in remnant populations of tawa forest at Mahoenui in the southern King Country (38'35S, 174’50'E) . In August 1990 about 240 hectares of gorse habitat was purchased by the Department of Conservation in this area as a reserve for these wetas. In this area with is mostly steep (>21 O) slopes with north- to east-facing aspects, a combination of cattle, goats and gorse bushes has set up a unique habitat for the weta. Cattle have established trails and tunnels in the undergrowth by pushing through the gorse bushes. The trails allow more light in which promotes fresh green growth, and also allows access for wild goats to browse on gorse and other plants in the area. Browsing by the goats crops the gorse bushes into dense “hedges”, and these spiny fortresses provide sanctuary from introduced predators for the weta. Adult females are very susceptible to predation from hedgehogs, possums, rats, cats and stoats when they come down to the ground to lay eggs. Also because of the danger that a fire could wipe out the entire Mahoenui Giant Weta Scientific Reserve a number of weta have been trans located to other areas.
Deinacrida mahoenui are unique amongst the giant weta species in having two different colour morphs. Although most of the Mahoenui weta (69%) tend to be a dark brown mahogany colour, 31% are a lovely yellow, and one female was even discovered with mahogany for half of her body and the other side to be yellow. Females are larger than males, with adults measuring up to 75mm and 50mm respectively. Females have been weighed at up to 19g and males up to 12g. The total life cycle (22 – 24 months) of Deinacrida mahoenui is short compared to some tree weta which live for up to 12 years in captivity.
Eggs are laid in the soil in autumn and incubation takes about 10 months. The first nymphs start emerging around March or April of each year. In the first 4 months after hatching the young weta literally “grow out of their skin” every month. Their exoskeleton is shed every month until August, then every 2 months until February. Mahoenui Giant Weta shed their skin, or moult, ten times throughout their life and each stage is called an instar. In the first 6 instars, if the young weta have broken off a leg or antennae the appendage can slowly grow back during each moult. But this ability to regrow limbs wanes in the latter instars. Once the weta reach maturity in autumn each year the females emit pheromones in their droppings. Males follow the scent until finding a female. The male will check if the female is ready for mating by rubbing his antennae all over the female. If she is ready she will stay still and they will mate. Once the females lay eggs, all the adults will die before winter. Females have a long ovipositor which looks like a spike at the end of their body. They use the ovipositor to lay between 200 and 400 eggs up to 23 mm below the surface of the soil. Each egg is a little vertical cylinder about 7mm long, and when the young nymphs’ first hatch out they are only 8mm long. Young nymphs are cannibalistic and like to eat other insects including caterpillars, spiders, cicada and crickets while they are growing rapidly. They also eat leaves, bark and dead leaf litter. Because of their cannibalistic diet, Mahoenui Giant Weta are generally solitary insects. If an intruder enters their territory they make warning sounds by extending their abdomen in and out to create clicks or by striking their hind legs against their abdomen to create a rasping sound. They will attempt to push or scare off predators by quickly raising their spiny hind legs.
The Department of Conservation held "The 'Big is Good' weta workshop" at Mitre 10 Mega, in the Valley. New Plymouth on Sunday 9 September 2012. Here one could see the giant weta from Mahoenui and build a weta hotel for the tree wetas in ones own garden. Below are a few photos of that event.
Constructing the weta houses
Visit this link for plans to build a weta house
Waitomo Education Service.
Barrett, P. (1991) Keeping Wetas in Captivity, Wellington Zoological Gardens Pub., Wellington. Meads, M. (1990)
The Weta Book – A Guide to the Identification of Weta, DSIRLand Resources, Lower Hutt. Sherley, G. H. & Hayes, L. M. (1993) The conservation of a giant weta at Mahoenui, King Country: habitat use and other aspects of its ecology, New Zealand Entomologist Vol. 16: 55-68.