XIII CROTALINAE 649 



The etfeet of the poison of liaUle-Snukes has Ijeen discussed 

 on p. 589. 



C. horridus is the connnon llattle-Snake of the United States ; 

 C. conjluentus is the species in AVestern and C. durissvs the 

 common species in South -Eastern North America. Very large 

 Eattle-Snakes, C. durissus, attain a length of 8 feet, others not 

 often more than five. They prey chiefly upon small Mammals, 

 hunting fm- tliom at night. Tn the daytime they are also 

 about, mainly in (irdor to l)ask. Although they occasionally 

 take to tlie water in pm-suit of their prey, they dislike being 

 wetted l)y 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 I'rairie-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 

 hiljernate under ground, often in considerable numbers. 



Piattle-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 loutl 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 vi1>ra- 

 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-liands ; 

 the under surface is yellowish ; the end of the tail is blackish. 

 The supra-ocular shields are smooth and much naiTOwer than the 

 scaly space between them, and there is only one pair of inter- 

 nasals. 



C. durissus s. adaviantcus differs from the previous species 

 chiefly by possessing two pairs of internasals ; and the dark 



