HABITS 103 



one another. The same thing probably takes place 

 in the African genus Dasypeltis, in which we find a 

 similar arrangement of the scales, though to a less 

 degree. 



The best known sounding apparatus is that of the 

 Rattlesnakes, described on p. 20. When alarmed, 

 these snakes gather the body in a few coils or roll 

 themselves up in a spiral, with the tail erect in the 

 centre, and vibrating with great rapidity, whilst the 

 head is ready for attack. Other snakes, such as the 

 Ancistrodon and some species of Coluber and 

 Zamenis, when excited, vibrate the tail in the same 

 manner ; but, being deprived of the sound-producing 

 apparatus, this expression of their anger does not 

 attract the same attention. It is from such a habit, 

 however, that the rattle must have been evolved and 

 perfected, not necessarily in a Lamarckian sense, but 

 through the different steps by which evolution or 

 creation has proceeded ; Natura non fecit saltics, as 

 Linnaeus well said. Many suggestions have been 

 made as to the use of the rattle. One of them is 

 that the rattling resembles the sound made by 

 locusts, and serves to decoy insect-eating birds ; 

 another, that it serves to call the sexes together. 

 Probably it is useful to the snake as a warning to 

 keep off disturbers which cannot serve as food, and 

 thus prevents useless expenditure of venom, or even 

 the breaking of the fangs. At any rate, it gives ex- 

 pression to the snake's excitement, as does the voice 



