Boa, a name loosely applied to any large snake that kills its prey by crushing. Properly the term is confined to serpents of the family Boidae (from tropical America and the Eastern Archipelago), distinguished from the pythons of the Old World by the absence of teeth on the premaxillas, and by the single row of inferior shields on the tail. The boas have an enormous gape, and the small teeth all point inwards. The tail is prehensile, and the rudiments of hind limbs which end in horny anal spurs assist these animals to suspend themselves from branches of trees whence they swoop down on their prey, which consists of small mammals; rats, according to Wallace, being their favourite diet.
In captivity they are fed on ducks, pigeons, and guinea-pigs, and after a meal they require a long period of digestion. The young are extruded alive, the eggs being hatched within the parent. "The largest species is the Anaconda (q.v.). The common boa (Boa constrictor) is said to attain a length of 20 feet, and specimens of from 12 to 14 feet are often met with. The colour is a reddish-grey with wavy longitudinal stripes. Wallace (Travels on the Amazon) says that boas "are not at all uncommon, even close to the city (Para), and are considered quite harmless. They are caught by pushing a large stick under them, when they twist round it, and the head being cautiously seized and tied to the stick, they are easily carried home."