Scientists in Australia say they fear native tarantulas are being driven to extinction by the booming trade in the giant spiders as household pets. Scientists are afraid that some species of Australian tarantula may have already disappeared.

Tarantulas are the world's biggest spiders, with legs spanning up to 15 centimeters. They are found throughout most of the warmer parts of the world. However, in tropical northern Australia, experts say so many have been caught to fuel the lucrative trade in these predators that the existence of certain species is now in doubt.

The bristly creatures may not be everyone's idea of a pet, but collectors say they are fascinating, so much so that they're being sold for hundreds of dollars apiece in pet shops across Australia.

Stuart Douglas breeds spiders to study their venom. He believes greedy poachers are destroying many pockets of tarantulas in the wild. "They're actually going into the environment and they're not leaving one spider behind," he said. "They're taking everything. Some of these spiders have adapted to live in one certain valley and if someone finds that valley and they come in and take everything that's it. You know, I can be pretty sure in telling you that there are extinct species of tarantula, through human greed, I suppose."

Robert Raven is a leading authority on tarantulas in Australia. He said some Australian species being sold in pet shops are so rare they have not been scientifically described yet.

He does not think tarantulas make suitable household pets, and apparently the spiders agree with him. Dr. Raven said they dislike being in captivity. "People don't realize also that they can climb glass, so even the best aquaria just a little bump on the aquaria a little gap the spider gets in and puts its leg in a starts prying it open. They'll get out and start walking around and they'll do more damage than you want to know about before you've controlled them."

Tarantulas are predators, and will eat almost anything they can kill, including crickets, most beetles, earthworms and moths. Larger spiders can even kill small reptiles and mice.

All tarantulas are venomous, although the bites are rarely dangerous to humans. The hairs on their abdomens are extremely fine, and can cause severe irritation to the skin and eyes.

Here in Australia they are not protected if found on private property, and they can legally be sold. But scientists say the law is increasingly being flouted on public land, by collectors keen to cash in on the spiders' popularity.