The Tarantula, Reappraised

News and commentary about environmental issues.
March 20 2012 12:55 PM

Hairy Cannibals

The tarantula, reappraised.

Tarantula.
Tarantula

Hemera Technologies.

More revolting creatures: the eel, the centipede, the skunk, the snapping turtle, the vulture, the tick, the jellyfish, the hyena, the slug, and the mosquito.

Movies have failed miserably at enlightening the public about tarantulas. Case in point: a villain in the first James Bond movie (Dr. No) puts a tarantula in our hero's bed. As Bond wakes to see the stocky black spider crawling on his shoulder he appears to be sweating heavily—presumably because this creature could kill him.

But the tarantula's bite is no more deadly than a bee sting. It was never the spider’s intention to bite Sean Connery, obviously too big to eat. The creature’s small mind was on how to get back to its familiar burrow, and Bond had more to fear from the cigarettes he smoked. (It was 1962.)

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Tarantula venom serves to subdue small prey—mainly insects; it actually takes considerable effort to get a tarantula to bite a human being. We know that thanks to the considerable efforts of the late Dr. William J. Baerg, who, while a member of the University of Arkansas entomology department during the 1940s, laboriously persuaded many tarantulas to bite him. The first attack was unbidden and occurred when the doctor tried to position a Trinidadian tarantula (Avicularia velutina: “extremely pugnacious in attitude,” he wrote, “it at first impressed me as probably venomous”) to bite a white rat. The spider went for his finger instead. Contrary to the prevailing wisdom, he learned that the sting, though irritating, was basically harmless. More deliberate attempts soon followed with 26 less pugnacious tarantula species. Baerg had to repeatedly prod them to bite. (For comparison’s sake, he also allowed himself to be bitten by the smaller and less scary-looking black widow spider, and got very sick.)

Of course it’s the tarantula's size and disconcerting hairiness that lead us to our prejudice. The biggest of the 932 named tarantula species, the Goliath bird spider of South America, is almost a foot across—an undeniably impressive specimen that can eat small vertebrates. (It is itself eaten, said to taste like shrimp.) At the other end of the scale is one (Aphonopelma paloma) with a body length of 8 mm, about 1/3 of an inch. About one-fifth of all spiders are tarantulas.

There is no record of any human being ever being killed by the sting of a tarantula, large or small. (There may be an unrecorded serious outcome somewhere for a person allergic to stings of any kind, or someone who suffered a bacterial infection from an untreated bite.) In any case the chances of a North American coming fact-to-face with a tarantula, let alone being bitten, are small. Tarantulas live in tropical or semi-tropical regions, and deserts around the world. In the U.S. there are about 40 species, mostly in Southwestern deserts, and none east of the Mississippi. (Some of the arboreal species, from Asia and South America, are faster-moving and pack a more painful bite.)

In late summer in the desert it is possible, though not common, to see males on the move seeking females. But most of the time the North American tarantulas stay out of people’s way, emerging from their burrows after dusk and retreating at dawn. Unfairly maligned by the public, the tarantula has also been looked down on by entomologists. Beside the orb-weavers like the famous Charlotte, tarantulas seem primitive, clumsy, and less than inspired in their silk work. Their name isn’t even their own—it comes from the European wolf spider (Lycosa tarantula), a different hairy creature. When Europeans came across new types of spiders in the Tropics, they designated any large, fuzzy ones as a kind of tarantula. It’s more accurate to call them Therasophids.

The startling hairiness is useful, an excellent adaptation for a creature with terrible eyesight. (Unfair that they have eight eyes, and not one works well.) Tarantulas’ hairs are sensitive to air movement, allowing them to detect something as subtle as the breeze caused by a cricket passing by, and to vibration, alerting them to a potential mate drumming on the ground off in the distance.

Another kind of hair acts as a line of defense, short of biting, for many New World spiders. When threatened these tarantulas use their legs to rake small, barbed hairs off the tops of their bellies. The hair defense is adapted to irritate the nasal passages and eyes of a mouse. Dr. Baerg’s wife Eloise, a good sport, got a temporary rash when she exposed her arm to a cloud of the hairs; other human beings approaching an agitated tarantula report inflamed eyes.

The tarantula does not stalk; it waits to sense something edible passing by. A female may spend her life, up to 30 years, within a couple of feet of her first home. In fact, tarantulas, the terrestrial ones anyway, are among the most sedentary of creatures. If James Bond's chest appeared moist in the spider scene from Dr. No, that's because an off-screen insect wrangler was misting the animal to make it crawl. (Tarantulas are extremely sensitive to water spray and air currents.)

When dinner wanders by, the spider seizes its prey—crickets, grasshoppers, beetles, flies, and roaches—with its short forelegs, known as pedipalps, and then impales it with upraised fangs. The venom at the tip of the fangs stuns or kills the future meal. Up close, or magnified, it is a scary technique.

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