'Dinosaur' of insects is saved from extinction

NEW Zealand scientists believe they have saved the world's heaviest insect - the giant weta, which is unique to these South Pacific islands - from the threat of extinction.

The giant weta, scientifically known as Deinacrida rugosa, is closely related to the cricket, grasshopper, and locust. It can grow as big as a man's fist in its two-year life span and weighs up to 78 grams (nearly 3 ounces).

It is the ''dinosaur'' of the grasshopper family, one of the few prehistoric animals that have survived millions of years, says Mike Meads, an entomologist.

The future of the giant weta has been assured, Mr. Meads says, by what he believes is the world's first translocation of an invertebrate.

He moved 43 of the insects from their native Mana Island, off Wellington, in 1977, in a bid to save them from predators. They were reestablished on remote Maud Island, in the Marlborough Sounds at the northern tip of New Zealand's South Island, where recent checks proved they were thriving.

''It's something that has never been tried before,'' said Meads, who works with the ecology department of the New Zealand government's Department of Scientific and Industrial Research. ''We have saved birds before by translocation, but no one has tried to save insects.''

Concern for the giant weta - a slow-moving noctural insect which, unlike its tree-dwelling New Zealand cousins, hugs the ground - arose when an experimental farm was established on Mana Island. With boats calling regularly, it was only a matter of time before rats were introduced on the island - and the giant weta was inevitably wiped out.

Already, rats, stoats, sea birds, and other predators have virtually destroyed the giant weta populations on the two other offshore islands on which they had been found.

When Meads first returned to Maud Island in 1978, a year after he moved the 43 giant wetas there, he found only one. In the next two years he found two.

But late last year, when several life cycles had passed, he found 12 - a mixture of adults and one-year-olds, showing that a thriving population existed in the long grass, bracken, and low bushes that cover the tiny island.

More important, they had survived the potentially destructive discovery of a stoat on the island last year. Eight stoats in all were found in an emergency wipeout operation mounted by scientists, who say there is now no sign of the predators.

Meads says that because of its evolution the giant weta has no defense mechanisms. It does not have any of the aggressive tendencies of its more common smaller cousins, whose teeth can give a sharp bite to a human being disturbing one in a wood pile.

The giant weta is safe from only one of the predators that trouble the smaller varieties - the field mouse. ''That's only because they are larger than mice, who are not game to have a go at them,'' says Meads.

The Maud Island experiment has given a big boost to conservation efforts for other species.

Meads says that in the past most conservation work on threatened species has been directed at breeding them in captivity and then releasing them into the wild.

But this is difficult, especially with insects, Meads says, because so little is known about their life histories. Translocation is less time-consuming - and it works.

He hopes his work with the giant weta will encourage other efforts to save threatened species, saying that in the past New Zealand had probably lost rare birds and invertebrates that it did not even know existed.