CRICKETS AND EARWIGS 153 



large number of little hard ridges, giving it the appear- 

 ance of an extremely fine file. These are much too small 

 to be seen with the naked eye, but a moderate magnifica- 

 tion, coupled with careful focussing, soon brings them into 

 view. When the chirping is to be produced, the insect 

 bends the fore part of the body slightly downwards, and 

 then slightly raising the fore wings, rubs them rapidly 

 across one another. During this motion, the file of one 

 rubbing against the surface of the other produces a 

 creaking vibration, which is greatly intensified by the 

 clear open plates above-mentioned, which are therefore 

 called "drums." It will now be evident why the females 

 are mute: they have neither "file" nor "drum," and 

 hence are physically incapable of " singing." 



It is clear from the above that the chirping is in no 

 true sense of the word either a voice or a song, being 

 quite unconnected with the respiratory organs ; it is a 

 purely external and mechanical sound, comparable, as a 

 means of expressing sentiments, rather with the human 

 device of clapping the hands, or flipping the fingers, than 

 with the utterance of sounds with the mouth. Of course 

 it is not to be expected that an insect should make any 

 noise with its mouth other than that produced by eating, 

 since the mouth does not, as is the case with us, commu- 

 nicate with the breathing organs. The entrances to 

 these are in the cricket, as in all other insects, along the 

 sides, and any sound that might be produced in them by 

 the passage in and out of the air would be more strictly 

 comparable with the voice of vertebrate animals. Some 

 insects, as for example the common blue- bottle fly, are 

 able to produce a noise in this way, and may therefore be 

 truly said to possess a voice. But that is by no means 

 the rule, and the sounds insects produce are in general the 

 result of the friction of external parts upon one another. 



