1 88 Evolution and Adaptation 



as high as my head, where hundreds were around me, I 

 observed the females coming around the drumming males.' 

 He adds, 'this season (August, 1868) a dwarf pear-tree in my 

 garden produced about fifty larvas of C. pruinosa ; and I 

 several times noticed the females to alight near a male while 

 he was uttering his clanging notes.' Fritz Muller writes to 

 me from S. Brazil that he has often listened to a musical 

 contest between two or three males of a species with a par- 

 ticularly loud voice, seated at a considerable distance from 

 each other : as soon as one had finished his song, another 

 immediately began, and then another. As there is so much 

 rivalry between the males, it is probable that the females not 

 only find them by their sounds, but that, like female birds, 

 they are excited or allured by the male with the most attrac- 

 tive voice." 



In the flies the following cases are given by Darwin : — 



" That the males of some Diptera fight together is certain ; 

 for Professor Westwood has several times seen this with the 

 Tipulae. The males of other Diptera apparently try to win 

 the females by their music : H. Muller watched for some 

 time two males of an Eristalis courting a female ; they hov- 

 ered above her, and flew from side to side, making a high 

 humming noise at the same time. Gnats and mosquitoes 

 (Culicidae) also seem to attract each other by humming ; and 

 Professor Mayer has recently ascertained that the hairs on 

 the antennas of the male vibrate in unison with the notes of a 

 tuning-fork, within the range of the sounds emitted by the 

 female." 



In the crickets, grasshoppers, and locusts, the males " are 

 remarkable for their musical powers " ; and it is generally 

 assumed that the sounds serve to call or to excite the female. 

 In these forms the noise is made by rubbing the wings over 

 each other or the legs against the wing-covers. 



In some of these forms both sexes have stridulating organs, 

 and in one case they differ to a certain extent from each 



