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Trap-Door Spider, common name for any of several large, hairy, harmless tropical spiders that nest underground. They make long burrows in the earth, line them with silk, which they spin, and fashion at the entrance a bevel-edged, hinged, accurately fitting trapdoor often made of alternate layers of earth and silk. The upper surface of the door may be covered with earth or gravel, thus disguising the entrance. A species common in the southwestern United States digs holes about 2.5 cm (about 1 in) in diameter and sometimes 30 cm (12 in) in length.
The nests of trap-door spiders are generally in groups. The young hatch in the burrows of their mothers and live there for a few weeks; they then leave the nest and begin small underground burrows of their own. Trap-door spiders subsist largely on ants and other insects.
Scientific classification: Trap-door spiders make up the family Ctenizidae of the order Araneae. The species common in the southwestern United States is classified as Bothriocyrtum californicum.