STRIDULATING ORGANS AND THE EAR. 



•9 



transverse ridges like a file. These ridges are also shown ; 

 their armature varies in the different species. On the 

 inner margin of the wing is a hardened and elevated 

 space or scraper, hence each upper wing is provided with a 

 file and a scraper, the latter covered with short and 

 stiff bristles. Fig. 48 shows the scraper at s, and the 



Fig. 48. — Stridulating organs (file and scraper) of Gryllus abhreviatus. A, 

 dorsal surface; s, scraper formed of bristles; B, ventral surface; f, file. Original. 



files at f. By elevating the upper wing at an angle of about 

 forty-five degrees with the body, the scraper of one wing 

 rests on the file of the other, and by moving the wings thev 

 rasp on each other. The sound is strengthened by the 

 vibrating wings, which act as sounding-boards. The illus- 

 trations (Fig. 48) show the organs greatly enlarged. If 

 insects produce sounds they must be able to hear them, 

 otherwise the male locusts, grasshoppers and crickets would 

 sing in vain, and we find in many cases in both sexes of 

 those insects, organs that have most probably a function 

 very similar to that of our ears; but we must not look for 

 such organs where we are apt to expect them to be. The 

 locusts have their ears on the first joint of the abdomen 

 (Fig. 37), while the grasshoppers and crickets have them 

 near the upper part of the front tibia? (Fig. 37 and 174, c-f). 

 All three families of stridulating orthoptera raise the 



