Its name is Wētāpunga – named for the God of Ugly Things. But beauty is in the eye of the beholder and some would say our giant wētā is a beautiful insect. No-one can deny it’s a monstrous one – the wētāpunga is possibly the heaviest adult insect in the world.
There are 70 species of wētā, including 11 species of giant wētā in Aotearoa. The wētāpunga is our ‘giant of giants’. They’re also a ‘dinosaur’ or ‘living fossil’ of sorts, because wētā are as ancient as the tuatara – they’ve been around for 190,000,000 years.
The largest confirmed weight for a wētāpunga (Deinacrida heteracantha) is 71 grams, but most weigh less than half that, ranging from 9 to 35 grams (that’s heavier than a sparrow). There are some potential rivals among the elephant beetles and goliath beetles of the world (they commonly exceed 50 grams), but the giant wētā holds the heavy-weight title for now. In fact, the giant wētā’s biggest rival – the reason it’s the world’s heaviest adult insect, not just ‘heaviest insect’ – is a big fat insect larva – the 115 gram immature offspring of the goliath beetle. It’s not called Goliathus goliatus for nothing.
It’s a pretty good bet that our record-breaking wētāpunga was a girl – females are much bigger than males – and the record-breaking weight may have been because she was carrying eggs at the time. Average body length is around 75 mm (3 inches) and these big, stocky members of the Cricket Order are arboreal forest dwellers.
Until recently, wētāpunga were found only on Hauturu/Little Barrier Island – an area of only 3,083 hectares (7,620 acres). They’ve now been translocated to other predator free islands as well as an ‘insurance’. But historically they were found in forests in all of northern New Zealand including Northland, the Auckland region and the Hauraki Gulf islands. Their habitat range on Little Barrier Island is from second-growth forests located on the lower slopes of the island to the mid-level tall kauri forest. The second-growth forest is dominated by silverfern, nikau palm, mahoe, and kohekohe.
Adult wētāpunga live a solitary, nomadic lifestyle, with most of their movement and feeding occurring at night. They can be found above ground level under loose bark or in the cavities of mahoe and pohutukawa trees. Wētāpunga feed on fresh leaves and prefer native plants with large leaves such as karaka, karamu, māmāngi, māhoe, and kohekohe.
Males tend to move farther than the females. At night a male will sometimes follow a female, staying back about 25 cm from her.
Giant wētā can live up to two years. Eggs take 125 days on average to hatch, then hatchlings go through 10 instar stages until adulthood – that’s one instar more than other wētā species.
Having 10 instar stages means that wētāpunga shed their entire exoskeleton a total of 10 times during their lifetime. They need to moult their rigid exoskeleton in order to get bigger. That extra instar makes the nymphal period longer and ultimately leads to their larger overall body size.
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 and six weeks.
Adult wētāpunga only live for about 6-9 months, during which time they will mate repeatedly. The females lay many groups of eggs in soft soil on the forest floor, generally producing between 100 to 300 cigar-shaped eggs in their adult lifetime.
Being big in the insect world can make you an attractive meal to mammal predators. While wētāpunga were commonly seen on Hauturu/Little Barrier Island in the 1950s, numbers have declined strongly since then, with predation rather than habitat destruction regarded as the main cause. Feral cats were present on the island until they were completely eradicated in the 1980s and may have fed on vulnerable juvenile wētāpunga.
An increase in the kiore population occurred after the feral cats were eradicated. Kiore are one of the giant wētā’s top predators, preying mostly on juvenile wētās which they kill during the night. The giant wētā finally got a bit of a break in 2004 when kiore too were removed from Hauturu. The wētāpunga population size grew back each year and a four-fold increase was reported six years after the kiore removal.
Native species also enjoy a hearty meal of wētāpunga. Tuatara, geckos and the North Island brown kiwi hunt wētāpunga during the night, and kingfishers, saddlebacks and the long-tailed cuckoo by day.
Fortunately for the future of our gentle giants, a captive breeding programme has been operating since 2008. Individuals captured on Hauturu/Little Barrier Island have been successfully bred in captivity, initially at Butterfly Creek.
The breeding project was joined by Auckland Zoo in May 2012 when staff captured 12 adult wētāpunga from Hauturu o Toi / Little Barrier Island and returned them to purpose built facilities at the Zoo. Following lots of mating and egg laying activity, hundreds of baby wētāpunga began hatching in early 2013.
The wētā were housed in purpose-built facilities at Auckland Zoo and reared both individually and in groups. So many hatched that extra staff were brought in to help feed the many hundreds of growing wētāpunga with fresh foliage. There were so many that as well as rearing them in separate containers, many had to be reared in groups in larger cages, which had not been attempted before in the breeding programme. Both methods of rearing were successful and produced a range of different sized wētāpunga for release.
Since 2012, Auckland Zoo has bred and released more than 4,000 onto pest-free islands in Auckland’s Hauraki Gulf, including The Noises, Motuora and Tiritiri Matangi Islands. Adults from Hauturu/Little Barrier Island have also been transferred directly to Motuora.
It is hoped that the released wētāpunga will eventually build up self-sustaining populations on these additional predator free islands. In 2016 an adult female was observed on Tiritiri Matangi Island in the area where the first population was released. She can only be a descendant of the initial translocated population of 25 individuals released in 2011. Individuals translocated onto Tiritiri Matangi island in 2014 have been observed mating.
Who knows, in years to come with a predator free life expectancy and food-rich habitat, perhaps that 71 gram record will be broken by an even bigger female ‘God of Ugly Things’.