Little Known Tarantula Traits

The tarantulas found in the Southwest are big enough to strike terror in the heart of the mother of a teenage naturalist, but they are dinky compared to some found in South America.

Quarter-Pound Spiders

“The one I studied for my masters thesis is the largest in the world,” he says. He has captured some with a 10-inch leg span, and they tipped the scales at a quarter of a pound. There have been reports of some as large as 12 inches, he says, but he has never seen one quite that big.

Like their cousins to the north, these giant spiders can repel an adversary with “really ferocious hairs,” Marshall says.

Apparently, having that kind of equipment eliminates the need for a toxic bite, because their fangs are particularly benign. The most hyperactive tarantulas are in Africa. Marshall has some in his lab, and he says all you have to do is prod them with a plastic tube and “they rear up and begin attacking the tube almost right away.”

Another species from southeast Asia goes into some kind of a dance whenever it feels threatened.

“If provoked, it rocks back and forth,” he says. “That’s something none of the other spiders did.” It’s unclear at this point what all that means, he adds. “Maybe they’re just trying to look more dangerous, like ‘I’m ready to fight,’” he says.

If Looks Could Kill

North America’s tarantulas have a limited range. They do not occur naturally east of the Mississippi River, and are found no farther north than Missouri, Marshall says. They are not without enemies. A black and orange wasp, known in Arizona as a “tarantula hawk,” can paralyze a tarantula with its sting. Then it lays its egg on the spider, and when the young wasp hatches it burrows into the paralyzed tarantula and feeds on it.

It’s a jungle out there, and in many ways the tarantula seems poorly equipped to survive. It has a very primitive respiratory system, Marshall says, so if it tries to run away it won’t get very far until it runs out of breath and collapses.

It doesn’t have much of a bite, but it does have those obnoxious hairs.

And nature gave it one other defensive mechanism: An awesome appearance that would make just about anyone think twice before picking it up.

Lee Dye’s column appears weekly on ABCNEWS.com. A former science writer for the Los Angeles Times, he now lives in Juneau, Alaska.

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