xn] STRTDULATIOK 105 



CHAPTER XII 



STRIDULATION 



MANY of the Arthropoda the large group which 

 includes insects and crustaceans as well as Arachnida 

 -are able to produce sounds, a fact familiar enough 

 in such insects as crickets and grass-hoppers. As, 

 however, the breathing apparatus of these animals is 

 entirely different from that of mammals and has no 

 connection whatever with the mouth and alimentary 

 canal, the mode of sound production is not at all the 

 same. Instead of setting vocal chords in vibration 

 by the expulsion of air through the larynx, insects 

 "sing' : or "chirp" by rapidly rubbing together 

 certain specially roughened surfaces, which constitute 

 what is called a "stridulating organ." In crickets, for 

 instance, each tegmen or wing-cover is provided with 

 a kind of file, and when the wing-covers are rapidly 

 vibrated, the edge of each rubs against the opposite 

 file, and a loud shrill sound is produced. 



The stridulating apparatus is by no means always 

 in the same place ; the thorax may rub against the 

 abdomen, the leg against the wing-cover, or one of 

 the mouth appendages against another. Nor are 

 the sounds produced always audible to human ears ; 



