tarantula, name applied chiefly to several species of the large, hairy spiders of the families Theraphosidae and Dipluridae of North and South America. The body of a tarantula may be as much as 3 in. (7.6 cm) long and, with legs extended, as much as 10 in. (25.4 cm) across. The North American tarantula, Dugesiella hentzi, has a leg spread of up to 6 in. (15.2 cm) and is common in parts of the SW United States. 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. Some Asian spiders are also called tarantulas, and there is a tailless whip scorpion genus Tarantula. Originally the name was applied to a spider of the wolf spider family, Lycosa tarentula, 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.