ANATOMY OF INSECTS INTERNAL 



43 



ways. Thus flies and bees buzz with their wings in rapid vibra- 

 tion, and the singing of the male cicada is produced by the rapid 

 vibration of a pair of membranes on the first abdominal segment. 

 Many beetles squeak by rubbing the wing-covers against some rasp- 

 like part of the body. But the grasshoppers and crickets are the 

 leaders in the insect orchestra. Grasshoppers often produce noises 

 in flying by rubbing 

 the hind legs against 

 the wing-covers or 

 by rubbing together 

 the front and hind 

 wings. Katydids 

 and crickets have 

 the best-developed 

 musical apparatus, 

 having a scraper 

 on the base of one 

 wing-cover and a 

 vein ridged like a 

 file on the base of 

 the other, which, 

 when rubbed to- 

 gether, vibrate the 



neighboring mem- FIG. 52. Ear of locust (Caloptenus italicus) seen from 



the inner side 



si 



T, tympanum ; TR, its border ; a, it, two bonelike processes ; 

 hi, pear-shaped vesicle ; ;/, auditory nerve ; ga, terminal gan- 

 glion ; st, stigma, or spiracle ; m, opening muscle, and ;#i, 

 closing muscle of same ; A/, tensor muscle of the tympanic 

 membrane. (After Graber) 



brane and produce 

 the strident song, 

 or the shrill chirp, 

 so characteristic of 

 these insects. 



That these sounds are heard by their mates is shown by the 

 answering call of one to another, and to similar tones produced 

 artificially. In grasshoppers a large auditory organ, or " ear," is 

 found on either side of the first abdominal segment. It consists of 

 a surface membrane, or tympanum, stretched over a cavity, on the 

 inner surface of which rest two processes, analogous to the small 

 bones of the human ear, which carry the vibration to a delicate 

 vesicle which connects with an auditory nerve. Similar small 

 membranes are found on the fore-tibia of certain insects and are 



