THE GRASSHOPPER 343 



HEARING 



As various insects produce noises of many kinds, we infer they must 

 hear, though definite evidence has not been forthcoming up to this time. 

 Flies and bees "buzz" by a rapid motion of the wings, while the singing of 

 the male cicada is produced by a rapid vibration of a pair of membranes 

 on the first abdominal segment, and a resounding drum-like membrane 

 within the thorax. Many beetles form a squeaking noise by rubbing 

 their wing-covers against some rasp-like portion of their body, while 

 grasshoppers rub their hind legs against the wing-covers as well as rub- 

 bing front and hind wings together. 



Crickets and katydids (Fig. 224) have a definite scraper on the base 

 of one wing-cover and a file-like apparatus on the base of the other. 

 These are rubbed together which causes the neighboring membrane to 

 vibrate and produce the "chirp." 



As such "chirps" or calls are answered by their mates, it must be 

 assumed that some hearing takes place. 



The grasshoppers have a large auditory organ on each side of the 

 first abdominal segment consisting of a surface membrane or tympanum 

 stretched across a cavity, on the inside of which two tiny processes some- 

 thing like the ear-bones of the frog are found. There are also similar 

 membranes on the tibia of some insects which may also serve as auditory 

 organs. 



A male mosquito will vibrate its antennae when a tone is produced 

 on a tuning fork of the same pitch as that made by the wings of the 

 female, so that it may be that in the mosquito the antennae have some 

 auditory function. 



THE MUSCULAR SYSTEM 



As in all animals possessing an exoskeleton the muscles must be 

 attached on the inner surface of the skeleton (Fig. 221). Each of these 

 muscles is innervated by nerves, however, just as in animals possessing 

 endoskeletons and move by a series of complicated pulley-like arrange- 

 ments as already seen in the crayfish. 



THE REPRODUCTIVE SYSTEM 



Among all insects there are two sexes, the male usually being the 

 smaller, more active and more brightly colored. It has been suggested 

 that the reason for this is that the handsomer males are thus able to 

 attract mates more often than those less handsome, and consequently 

 the young born of such more handsome fathers, were also handsome, 

 thus eliminating, by natural selection, the less handsome. It has been 

 suggested by some also that the female, who carries the eggs, by being 

 less gaudy in appearance is also less conspicuous, and therefore not so 

 likely to be caught by natural enemies. 



