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Deinacrida heteracantha

phylum: Arthropoda

class: Insecta

order: Orthoptera

family: Stenopelmatidae

status: Vulnerable, IUCN

range: New Zealand

Description and biology

Wetas are nocturnal (active at night) grasshoppers with extremely long antennae. The giant wetas are among the largest insects in the world, and the wetapunga is the heaviest of the eleven giant weta species. It can weigh up to 2.5 ounces (70.9 grams), making it the heaviest insect in the world. The body of an adult female wetapunga may measure 4 inches (10 centimeters) long. With its armored, spiny legs spread out, the insect may reach 7 inches (17.8 centimeters) in length. Males are smaller in size.

Wetapungas have rounded bodies that are various shades of brown in color. They lack wings. Behind their head lies a broad protective shield. This anatomical detail, which was present in some dinosaur species, indicates how primitive these insects are.

Like other weta species, the life cycle of a wetapunga lasts a little over two years. Wetapungas mate and lay eggs during all but the winter months. Mating and egg-laying are usually repeated many times over a period of several days. The male dies soon after the final mating. After laying all of her eggs, sometimes up to 400 in total, the female also dies.

The eggs are approximately 0.27 inch (0.69 centimeter) long and 0.08 inch (0.2 centimeter) wide. They are laid at a depth of up to 0.78 inch (1.98 centimeters) beneath the soil surface. During midsummer, some eggs hatch within three weeks. Most eggs remain undisturbed in the ground through the winter, hatching after nine or ten months. The newly hatched wetapungas, called nymphs, are pale, mottled miniature versions of the adults. During the two years it takes them to reach adulthood, nymphs molt (shed) their skins about 10 times.

Wetapungas are primarily vegetarian. They venture out at dusk to feed on the leaves of a variety of trees, shrubs, herbs, and grasses. They are preyed on by many animals, including cats, rats, pigs, hedgehogs, birds, tuataras, and lizards.

Habitat and current distribution

Wetapungas once inhabited the main New Zealand islands. Now, they are found only on Little Barrier Island, a small island lying off the northeast coast of North Island (of the main New Zealand islands). They are arboreal (tree- dwellers). They spend most of their time in kauri, pohutukawa, kanuka, and other broadleaf trees, seldom coming down to the ground.

History and conservation measures

Before humans began settling on New Zealand islands, bats were the only warm-blooded mammals in the New Zealand ecosystem. All species of wetas thrived in safety. Sometime between 1,000 and 2,000 years ago, native people from Polynesian islands (Maoris) first traveled to the New Zealand islands. They brought with them the kiore, or Polynesian rat. It quickly became a predator of wetas.

When European settlers began arriving in the eighteenth century, they brought to the islands an enormous array of other animals. They cut down the forests for timber and to create farmland, and the whole shape of the New Zealand landscape changed. Those lands that were not cleared were quickly overrun with rodents, deer, goats, pigs, and opossums. In the 200 years since the arrival of European settlers, over 80 percent of New Zealand's natural vegetation has disappeared.

All eleven weta species are protected by New Zealand law and their limited habitats have been designated as reserves. However, predators remain in these habitats. Although domestic cats that had been living in the wild on Little Barrier Island have been exterminated, the wetapunga is still threatened by the kiore.