BOA

any of about 60 species in more than a dozen genera of snakes comprising the subfamily Boinae of the family Boidae. Boas occur in both the Old and New World, chiefly in warm regions. They vary in length from about 20 cm (8 inches) to perhaps more than 7.6 m (25 feet) and have stout bodies and rather short tails. Most are terrestrial or semiaquatic; some are arboreal. Most have disruptive patternsblotches and diamondson their brown, green, or yellowish bodies. The young are born alive in the majority of the species, not in eggs. Boas bite their prey, then kill by constricting; a number have heat-sensitive lip pits for detecting warm-blooded prey. Folklore to the contrary, boas are not dangerous to humans. The boa constrictor (species Boa constrictor) occupies a variety of habitats from coastal northern Mexico and the Lesser Antilles to Argentina. (In popular usage any large snake of this kind is likely to be called a boa constrictor.) It is seldom more than 3.3 m (11 feet) long; the record is 5.55 m (18.2 feet). Several boas are arboreal and long-toothed for catching birds. An example is the 1.8-metre (6-foot) emerald tree boa (Corallus caninus) of tropical South America; the adult is green above, with white dorsal stripe and crossbars, and yellow below. The rainbow boa (Epicrates cenchria) of Costa Rica to Argentina is not strongly patterned but is markedly iridescent. The brown, 45-centimetre (18-inch) rubber boa (Charina bottae) of western North America is the most northerly boa and is a burrowing species that looks and feels rubbery. The 90-centimetre (35-inch) rosy boa (Lichanura trivirgata), ranging from southern California and Arizona into Mexico, usually is brown- or pink-striped. The 10 species of sand boas (Eryx) of northern Africa to India and central Asia are burrowers in drylands. Often called wood snakes and separated as the subfamily Tropidophinae are the two species of Trachyboa of South America and more than 10 species of Tropidophis, chiefly of the West Indies. See also anaconda.