tarantula (tərănˈchələ) [key], name applied chiefly to species of the large, hairy spiders of the family Theraphosidae of North and South America, Africa, S and SE Asia, and Australia. The body of a tarantula may be as much as 4 in. (10 cm) long and, with legs extended, more than 10 in. (25.4 cm) across. The largest tarantulas may kill small vertebrates, but their usual food is other arthropods. The bite of a tarantula may be painful but is not usually dangerous to humans. Most tarantulas found in the United States are members of the genus Aphonopelma, the largest of which have leg spreads of up to 6 in. (15.2 cm). The smaller Texas brown tarantula, A. hentzi, may be found in the W United States as far north as Colorado, Kansas, and Missouri.
The name tarantula is also applied to the purse-web spiders (family Atypidae) and funnel-web spiders (Dipluridae and Hexathelidae) of the Old and New World, and sheet funnel-web spiders or dwarf tarantulas (Mecicobothriidae) of the New World; there is a tailless whip scorpion genus Tarantula. Originally the name was applied to a spider of the wolf spider family, Lycosa tarantula, of S Europe, whose bite was supposed to cause tarantism, a nervous condition characterized by hysteria; the best cure was believed to be strenuous and prolonged dancing of the tarantella. Spider families are classified in the phylum Arthropoda, class Arachnida, order Araneae.