CROTALINAE 649 



The effect of the poison of Eattle-Snakes has been discussed 

 on p. 589. 



C. horridits is the common Eattle-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 

 Eattle-Snakes, G. 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, appropri- 

 ating as a rule those of ground-squirrels, rats, and Prairie- 

 dogs. The often-repeated story about Eattle-Snakes living in 

 neighbourly friendship in the holes of Prairie-dogs, together 

 with the little Prairie-owk, is an exaggeration. AVe 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. 



Eattle-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 vibra- 

 tions 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 inter- 

 nasals. 



C. durissus s. adamanteus differs from the previous species 

 chiefly by possessing two pairs of internasals ; and the dark 



