SELECTION AND COUKTSHIP. 267 



hand, are the antlers of the stag, the tusks of the boar, the 

 spur of the cock, and the hugely developed pair of jaws in 

 the male stag-beetle ; all are instruments employed by the 

 males in the struggle for the females, for annihilating or 

 chasing away their rivals. 



In the cases just mentioned, it is the bodily " struggle to 

 the death" which determines the origin of the secondary 

 sexual characters. But, besides these mortal struggles, there 

 are other important competitions in sexual selection, which 

 no less influence the structure of the rivals. These consist 

 principally in the fact that the courting sex tries to please 

 the other by external finery, by beauty of form, or by a 

 melodious voice. Darwin thinks that the beautiful voices 

 of singing birds have principally originated in this way. 

 Many male birds carry on a regular musical contest when 

 they contend for the possession of the females. It is known 

 of several singing birds, that in the breeding season the 

 males assemble in numbers round the females, and let their 

 songs resound before them, and that then the females choose 

 the singers who best please them for their mates. Among 

 other songsters, individual males pour out their songs in the 

 loneliness of the forest in order to attract the females, and 

 the latter follow the most attractive calls. A similar musical 

 contest, though certainly less melodious, takes place among 

 crickets and grasshoppers. The male cricket has on its belly 

 two instruments like drums, and produces with these the 

 sharp chirping notes which the ancient Greeks curiously 

 enough thought beautiful music. Male grasshoppers, partly 

 by using their hind-legs like the bow of a violin against 

 their wing coverings, and partly by rubbing their wing 

 coverings together, bring out tones which are, indeed, not 



