THE HOUSE-CRICKET 191 



like a file. When the cricket chirps he slightly raises 

 the wing-covers, and rubs them rapidly together. The 

 file of one wing- cover plays upon a roughened triangular 

 space, just behind the file of the other wing-cover, and 

 sets up a squeak, like that of a 

 fiddle-string touched with the bow. 

 The vibrations produce a trembling 

 movement in both wing-covers, and FlG 42> _ Part of the 

 it is probable that the clear space of male house-cricket, 

 becomes strongly agitated and en- 

 forces the sound. Usually the right wing- cover plays upon 

 the left, but the action can be reversed. An imitation 

 of the natural sound can be produced by moving the 

 wing- covers of a fresh-killed cricket with a pin. In the 

 female file, roughened surface and resonator are all want- 

 ing ; hence she is dumb, and unable to return the call of 

 her mate. 



In the large green grasshopper (not really a grasshopper) 

 of the south of England the sound is produced in much 

 the same way, though the details of the mechanism are 

 changed. But in the common grasshopper, which is a 

 totally different insect, belonging to another family, the 

 outer surface of the wing-cover is rubbed against the 

 inner surface of the thigh. A row of minute projections on 

 the thigh plays the part of the file of the cricket, and when 

 rubbed against the sharp edge of a prominent vein, throws 

 the wing-cover into active vibration. 



Many insects of the most diverse kinds are able to pro- 

 duce sounds. The commonest way is to rub a surface 

 roughened by close-set ridges against a projecting edge, 

 and the surfaces made to play one upon the other may 

 belong to almost any part of the body ; legs, body-seg- 

 ments, palps, proboscis, wing-covers and wings may be 

 employed for this purpose. In particular cases organs so 

 important as the wings or hind legs are altogether devoted 

 to sound-production, and rendered useless for ordinary 

 purposes. Sometimes it is the vibration of the wings 





