188 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 larva of C. pruznosa; and I 
several times noticed the females to alight near a male while 
he was uttering his clanging notes.’ Fritz Miiller 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 thére 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 
Tipulaz. The males of other Diptera apparently try to win 
the females by their music: H. Miiller 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 
(Culicidze) also seem to attract each other by humming; and 
Professor Mayer has recently ascertained that the hairs on 
the antennz 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 
