The largest grow to a length of thirty feet and upwards; but boas ordinarily do not attain more than twenty feet in length.
The Spotted Boa.
The boa scytale, or spotted boa, is of a greyish colour, marked with round spots, and scarcely inferior in size to the former.
The Ringed Boa.
There is another species—the ringed boa, or boa cenchris—which, though growing to a considerable size, does not attain that of the former species.
A curious species (the boa canina) has a large head, shaped somewhat like that of a dog; the general colour a bright Saxon-green, with transverse white bars down the back. The sides are of a deeper green, and the belly is white.
Wallace describes a small one only eleven feet in length, but as thick as a man’s thigh. It was secured by having a stick tightly tied round the neck. It went about dragging its clog with it, sometimes opening its mouth with a very suspicious yawn, and sometimes turning its tail up into the air. Being put into a cage, and released from the stick, it began to breathe most violently, the expirations sounding like high-pressure steam escaping from a Great Western locomotive.
The boa, however, is not much dreaded in South America, as it seldom or never attacks man; which the anaconda is said always to do, if it can find him unprepared. Stories are told of desperate encounters between travellers in the forests of the Amazon and pythons or boas. A French traveller narrates how, on one occasion, the whole of his attendants took to flight on seeing a huge python approaching,—with the
exception of a gallant native, who, attacking the monster vigorously with a long, lithe pole, struck it a blow which paralysed its powers; when, the party returning, it was easily killed.