Fig. 180.–Skull of a Rattle-Snake, Crotalus durissus. × 1. A, Lateral view, jaws slightly opened; B, ventral view; C, lateral view, the jaws opened fully in the position of striking; D, dorsal view. Compare this with the diagrammatic figures on p. [588], where the mechanism has been explained. Col, Columella auris; Cond, condyle; Cr (in B), sphenoidal crest for the attachment of the powerfully developed ventral cranio-cervical muscles; E.P, ectopterygoid or transverse bone; F, frontal; Max, maxillary; P, parietal; P1, post-orbital process; Pal, palatine; Pmx, pre-maxillary; Pr.f, prefrontal; Ptg, endopterygoid; Q, quadrate; Sq, squamosal.
The effect of the poison of Rattle-Snakes has been discussed on p. [589].
C. horridus is the common Rattle-Snake of the United States; C. confluentus is the species in Western and C. durissus the common species in South-Eastern North America. Very large Rattle-Snakes, C. durissus, attain a length of 8 feet, others not often more than five. They prey chiefly upon small Mammals, hunting for them at night. In the daytime they are also about, mainly in order to bask. Although they occasionally take to the water in pursuit of their prey, they dislike being wetted by rain, withdrawing then into their holes, appropriating as a rule those of ground-squirrels, rats, and Prairie-dogs. The often-repeated story about Rattle-Snakes living in neighbourly friendship in the holes of Prairie-dogs, together with the little Prairie-owls, is an exaggeration. We do not know how many of the original inmates are eaten. Pairing takes place in the spring. During the cold months they hibernate under ground, often in considerable numbers.
Rattle-Snakes have few enemies besides man and pigs. The latter kill and eat them wherever they can. The rattle is decidedly useful to the snake as an instrument of warning off any approaching possible enemy, since no snake likes to bite unless in self-defence or in order to kill its prey. The noise of the rattle is very loud in dry weather, much duller on clammy days; it is a shrill sound like that of a rattling alarm-clock, and a well-conditioned snake in a room can make conversation well-nigh impossible, and can keep on rattling for half an hour or longer. The rattle is kept in such rapid lateral vibrations that it shows only a blurred image, the rattle standing with its broader sides vertically, not horizontally. They endure captivity for many years, and become tame enough not to hiss and to rattle whenever they are approached.
C. horridus is grey-brown above, usually with a rusty vertebral stripe and with V- or M-shaped blackish cross-bands; the under surface is yellowish; the end of the tail is blackish. The supra-ocular shields are smooth and much narrower than the scaly space between them, and there is only one pair of internasals.
C. durissus s. adamanteus differs from the previous species chiefly by possessing two pairs of internasals; and the dark markings on the body form a handsome pattern of rhombs with lighter centres and yellowish edges. This is the largest species of Rattle-Snake, reaching a length of 8 feet.
C. confluentus has broader, transversely striated, supra-ocular shields. The specific name refers to the continuous series of large brown or red rhomboidal spots on the back.
Fig. 181.–Crotalus durissus s. adamanteus (Rattle-Snake). × ¼.