4GG PHYSIOLOGY. 



FIFTH CHAPTER. 



OF THE SOUNDS AND NOISES EMITTED BY 

 CERTAIN INSECTS. 



268. 



THE investigation into the sounds emitted by insects during their 



motions does not inappropriately follow the description of these several 



motions, for the causes of these sounds appear to exist in these motions 



themselves. It was formerly supposed that the majority of these sounds 



were produced by the motion of the wings alone, without taking the 



least consideration of the apertures that are found upon the body of 



the insect, and through which, upon every respiration, air streams in 



and out. The mechanical friction of the wings together, or of the 



latter against the thighs, were considered as the causes of the loud cries 



of many grasshoppers and locusts, and also the vibration of the air 



caused by the strokes of the wings was considered as all that produced 



the hum in the flight of bees, wasps, and flies. If even the friction of 



portions of the integument together, for instance, of the proiiotum upon 



the face of the mesonotum in many beetles is apparently the sole cause 



of the noises emitted by them, yet in the majority of other instances a 



mere mechanical friction is not suflicient to produce so strong and shrill 



a tone, for it is doubtlessly frequently the air streaming out of the stigma, 



and thereby putting vibratory bodies in motion, that produces these 



sounds : and just as easily as this is considered to be the cause of the 



noises emitted by the Cicada, may it also be proved to be that of 



die humming of the bees, wasps and flies. An experiment of this 



description is the theme of the present chapter : we therefore pursue 



the path, in our investigation of this subject, which nature seems to 



have traced, and shall commence with the sounds produced by mere 



mechanical friction, which will be followed by the hum heard during 



flight, and we shall conclude with such noises as are produced by 



peculiar organs. 



