Tarantula - Bites and Urticating Hairs

Bites and Urticating Hairs

Though all tarantulas are venomous, few species have been claimed to cause human fatalities, though some bites cause serious discomfort that might persist for several days. Despite their often threatening appearance and reputation, no tarantula has been known to have a bite that is deadly to humans. In general, the effects of the bites of all kinds of tarantula are not well known. While the bites of many species are known to be no worse than a wasp sting, accounts of bites by some species are reported to be very painful and to produce intense spasms that may recur over a period of several days; the venom by the African tarantula Pelinobius muticus also causes strong hallucinations. In all cases, it is advisable to seek medical aid. Because other proteins are included when a toxin is injected, some individuals may suffer severe symptoms due to an allergic reaction rather than to the venom. Such allergic effects can be life-threatening.

Before biting, tarantulas may signal their intention to attack by rearing up into a "threat posture", which may involve raising their prosoma and lifting their front legs into the air, spreading and extending their fangs, and (in certain species) making a loud hissing by stridulating. Their next step, short of biting, may be to slap down on the intruder with their raised front legs. If that response fails to deter the attacker, the tarantulas of the Americas may next turn away and flick urticating hairs toward the pursuing predator. The next response may be to leave the scene entirely, but, especially if there is no line of retreat, their final response may also be to whirl suddenly and bite. Some tarantulas are well known to give "dry bites," i.e., they may defensively bite some animal that intrudes on their space and threatens them, but they will not pump venom into the wound.

New-world tarantulas (those found in North and South America) are equipped with urticating hairs on their abdomen, and will almost always throw these barbed hairs as a first line of defense. These hairs will irritate sensitive areas of the body and especially seem to target curious animals who may sniff these hairs into the mucous membranes of the nose. Some species have more effective urticating hairs than others. The Goliath Birdeater is one species known for its particularly irritating urticating hairs. Urticating hairs can penetrate the cornea so eye protection should be worn when handling such tarantulas.

Old-world tarantulas (from Europe, Africa, Asia and Australia) have no urticating hairs and are more likely to attack when disturbed. Old-world tarantulas often have more potent, medically significant venom.

There are dangerous spider species which are related to tarantulas and frequently confused with them. A popular urban legend maintains that deadly varieties of tarantula exist somewhere in South America. This claim is often made without identifying a particular spider, although the "banana tarantula" is sometimes named. A likely candidate for the true identity of this spider is the dangerous Brazilian wandering spider Phoneutria nigriventer, of the family Ctenidae, as it is sometimes found hiding in clusters of bananas and is one of several spiders called the "banana spider." It is not technically a tarantula but it is fairly large (4–5 inches long), somewhat hairy, and is highly venomous to humans. Another dangerous type of spider that has been confused with tarantulas is the Australasian funnel-web spider. The best known of these is the Sydney funnel-web spider Atrax robustus, a spider that is aggressive, highly venomous, and (prior to the development of antivenin in the 1980s) was responsible for numerous deaths in Australia. These spiders are members of the same suborder as tarantulas. Some Australians use the slang term 'triantelope' (a corruption of the incorrect term 'tarantula', which is also used) for large, hairy and harmless members of the Huntsman spider family which are often found on interior household walls and in automobiles.