The Encyclopedia Americana (1920)/Boa

BOA, a serpent of the sub-family Boinæ of the family ../Boidæ/ (q.v.); specifically, Boa constrictor.

The boas include the largest living snakes, but most of the species are of medium or small size. Their muscular power in the typical forms is very great, enabling them to hang suspended, almost by the tail alone, from trees, and to seize and crush prey to death by swiftly coiling around it. Most of the 40 or 50 species in the sub-family are American, but some small species inhabit the warmer parts of Europe, Africa, Asia and Polynesia. Several of the tropical American boas are huge snakes, the water-boa (Eunectes murinus) occasionally exceeding 30 feet in length. (See ). They attain sexual maturity, however, long before completing their growth, and the females bring forth their young alive. These young snakes are completely formed, resemble their parents and are able at once to take care of themselves, yet do not for some time wander far from the mother. The American boas inhabit forests and climb to the lower branches of the trees, where they seek or await their prey, usually above a path. There the serpent swings about in the air till some luckless animal

then, suddenly relinquishing his position, he seizes the victim and coils his body instantly round its throat and chest. The folds are gradually tightened with enormous force and speedily induce death. The animals thus destroyed by the larger boas are sometimes as large as tapirs, deer and even bullocks, but ordinarily much smaller mammals and birds. Having crushed and rolled its prey until its bones are broken and it is compacted into the form of a sausage, the boa takes it into its mouth and slowly engulfs it, the action being facilitated by a copious flow of saliva; but there is no truth in the reputed preparation of the prey by a covering of slime, etc. It is doubtful whether an animal larger than a capybara or goat could be swallowed, even after crushing. The process of digestion is slow, and while it is proceeding the serpent is inert and easily killed or captured. Experience with large examples in captivity show that a full meal once in six months or so seems all they ask or need; and weeks elapse before the indigestible parts pass out.

Several of the larger species are well known and often seen in menageries, where they are easily distinguished by the dog-like shape of the head and by the well-defined patterns of the markings. These are exceedingly handsome in most cases, the colors being yellow buff, chestnut and varying browns, set off by black and white; and the skins, which may be tanned into good leather with the scales on, are of high commercial value for making purses, belts and other ornamental articles. Among the best known species are the common boa &mdash; the Boa constrictor proper (for that term is ignorantly given to all), which is one of the lesser forms, rarely exceeding 10 feet in length. Its home is the region of the Amazon and Orinoco rivers, and it is pale brown, with a chain-like series of dark-brown markings on each side of the spine, enclosing large oblong-oval spots, and a series of large dark spots along the sides, each with a light centre; on the tail the markings become brick-red. Several other species of this genus, some much larger, inhabit South and Central America. One, the imperial or rainbow boa (Boa or Epicrates, cenchris), about seven feet , long, is remarkable in that, although in the shade it appears a pale brown with darker rings, in bright sunshine its skin shines with marvelous iridescence. It is called aboma in Mexico, and is believed to be the serpent venerated by the ancient Mexicans and worshipped with bloody sacrifices. Two species of true boas inhabit Madagascar; and three species, all small and of burrowing habits, are to be found on the Pacific coast of the United States. One of these is the stubby little rubber-boa or &ldquo;two-headed snake&rdquo; (Charina bottæ), well known in California, which has amazing ability as a contortionist.

To a closely related genus (Eunectes) belongs the gigantic water-boa whose habits are almost aquatic. (See ). Tree-boas (genus Corallus) are confined to the forests of tropical America, except one species in Madagascar. They are long, slender serpents of abnormal habits, lightning-like in their quickness in catching birds and naturally savage in disposition; the color is brown except one bright-green Brazilian species. Another genus (Lichanura) has a few species that dwell in

the West Indies and Mexico, and are occasionally taken in Arizona and southern California; and small boas of this or an allied sort are frequently brought into our ports from Cuba, tightly coiled about bunches of bananas. The genus Eryx, containing small, active, burrowing snakes, belongs to the deserts of northern Africa and Asia Minor.