SEXUAL SELECTION 459 



world except in Soutli America, and here no less than four 

 genera occur. One of these, Elaps, is venomous, a second 

 and widely distinct genus is doubtfully venomous, and the 

 two others are quite harmless. The species belonging to 

 these distinct genera inhabit the same districts, and are so 

 like each other that no one "but a naturalist would dis- 

 tinguish the harmless from the poisonous kinds." Hence, 

 as Mr. "Wallace believes, the innocuous kinds have probably 

 acquired their colors as a protection, on the principle of 

 imitation; for they would naturally be thought dangerous 

 by their enemies. The cause, however, of the bright colors 

 of the venomous Elaps remains to be explained, and this 

 may perhaps be sexual selection. 



Snakes produce other sounds besides hissing. The 

 deadly Uchis carinata has on its sides some oblique rows 

 of scales of a peculiar structure with serrated edges; and 

 when this snake is excited, these scales are rubbed against 

 each other, which produces "a curious prolonged, almost 

 hissing sound. ' ' " With respect to the rattling of the rattle- 

 snake, we have at last some definite information: for Prof. 

 Aughey states," that on two occasions, being himself un- 

 seen, he watched from a little distance a rattlesnake coiled 

 up with head erect, which continued to rattle at short inter- 

 vals for half an hour: and at last he saw another snake 

 approach, and when they met they paired. Hence he is 

 satisfied that one of the uses of the rattle is to bring the 

 sexes together. Unfortunately he did not ascertain whether 

 it was the male or the female which remained stationary 

 and called for the other. But it by no means follows from 

 the above fact that the rattle may not be of use to these 

 snakes in other ways, as a warning to animals which would 

 otherwise attack them. Nor can I quite disbelieve the 

 several accounts which have appeared of their thus para- 

 lyzing their prey with fear. Some other snakes also make 

 a distinct noise by rapidly vibrating their tails against 



«3 Dr. Anderson, "Proo. Zoolog. Soc," 1811, p. 196. 

 6* "The American Naturalist," 1873, p. 85. 



