THE SPECIAL SENSES 381 



has on the upper surface of the first abdominal segment 

 a pair of tympana or ear-drums (Fig. 233), composed sim- 

 ply of the thinned, tightly stretched chitinous 

 cuticle of the body. On the inner surface of this 



FIG. 233. Grasshopper, showing auditory organ (a. o.) in first segment of abdomen. 

 (Wings of one side removed.) 



ear-drum there are a tiny auditory sac, a fine nerve lead- 

 ing from it to a small auditory ganglion lying near the 

 tympanum, and a large nerve leading from this ganglion 

 to one of the larger ganglia situated on the floor of the 



a.o 



FIG. 234. A cricket, showing auditory organ (a. o.) in fore-leg. 



thorax. In the crickets and katydids, insects related to 

 the locusts, the auditory organs or ears are situated in the 

 fore-legs (Fig. 234). 



Certain other insects, as the mosquitoes and other midges 



