Far greater and much more dreaded by the natives is the great water boa, or anaconda (B. murinus), of the Amazonian region, which is the longest of American snakes, and the worst foe of such river-loving creatures as capybaras and iguanas. The color scheme of the anaconda is greenish yellow above, with a single, or two alternating series, of large, blackish transverse spots, and one or two lateral series of blackish eyespots with white centers. The lower parts are whitish, spotted with black. The anaconda is very aquatic, and is usually found submerged close to the banks of the river, on the lookout for its prey. Although mammals and crocodiles are occasionally eaten by this snake, it prefers birds, these being constricted and eaten under water. Only a single instance of an anaconda having attacked a man is on record. Although it grows to a length of over thirty feet, it is sexually mature when about half that length.
Various very slender and agile species, the tree boas, belong to the tropical American forests, one of which is called the "rainbow" boa because of its marvelous iridescence in the sunlight. Another large species inhabits Central America and Mexico; and two small, brown secretive snakes, the "rubber" boas, more commonly known as "double-enders," because their blunt tails closely resemble their heads, are found in California and northward to British Columbia. The remainder of the family are scattered from Africa to the South Sea Islands.
ORDINARY SNAKES (COLUBRIDÆ)
We now come to the family Colubridæ, which embraces nine-tenths of all the modern serpents of the world. The more hardy species are to be found north to about the summer isotherm of 41 degrees; and snakes are absent only from some of the South Pacific Islands, New Zealand and Ireland; Ireland never had any, despite the St. Patrick legend.
The best arrangement of the Colubridæ is that by Boulenger, who, adopting Duméril's terms, has divided them into three series according to the character of the teeth.
1. Aglypha—All the teeth solid and not grooved. Harmless, that is, not venomous.
2. Opisthoglypha—One or more of the posterior maxillary teeth grooved. Mostly poisonous; a few tropical species.
3. Proteroglypha—Anterior maxillary teeth grooved or tubular. Deadly poisonous; cobras, coral snakes, etc.
The immense family Colubridæ is divided into several subfamilies, the first and most extensive of which is the Colubrinæ, in which are associated all the "harmless" snakes in the world except the boas and pythons. None exceeds twelve feet long, and most of them are much smaller. Nearly all lay eggs, but some bring forth large broods of living young, among which are our water snakes, and the striped "garter" and "ribbon" snakes so numerous in our meadows and gardens. These striped snakes (Eutainia) exist in a great number of "species" or varieties most confusingly varied in coloring, some having no stripes whatever. They are very hardy, living far toward the north in Canada, and are the last to go into hibernation and the first to reappear in spring. For this winter sleep they burrow deeply into soft soil, or where rocky places exist, seek deep crevices.
The water snakes of the genus Tropidonotus follow, with many representatives in all temperate countries, one of which is the "common grass snake" of England—the only serpent in Great Britain except the viper and a rare little burrower. Ten species, with several varieties, are credited to the United States, some of which are ringed with irregular or broken bands of blackish on gray, others obscurely blotched, and some black or brown with red bellies. They are the ugliest of all our snakes both in appearance and in vicious temper; and are of no service to mankind, for their food consists entirely of fishes, frogs, toads, etc., obtained in or near the water. They live altogether in rivers, ponds and swamps; and by their dark bodies, flat heads, and keeled scales so resemble moccasins whose fierce, repellent attitudes they imitate, that in the South they are almost as much feared; hence it is well to note the differences. The harmless water snake is more slender than the deadly moccasin and may be told by the red spots on the abdomen; the undersurface of the poisonous snake is straw color, with black or gray spots on younger individuals, but has no red spots. The water snake has the plates on the underside of the tail in two rows, the moccasin in a single row. These snakes are agile swimmers and are able to spend a long time in hiding under water. They produce their young alive in broods of twenty-five to fifty, and they are as pugnacious as their elders.