274 INSECT ARTIZANS AND THEIR WORK 



on the stones, and was presently able to convince 

 my friend that the sound came from them." 



Many insects make minor sounds, perceptible 

 only to their own kind or to observers who come 

 into pretty close touch with them. Such is the 

 stridulating of ants, which is effected by the seg- 

 ments connecting the thorax and the hind body. 

 Many of the beetles also stridulate, but they do 

 not produce notes comparable in volume with 

 those of the Cicadas and the Grasshoppers. The 

 apparatus varies a good deal. 



The large tropical beetles known as Passalids, 

 though they are without such apparatus in the 

 perfect state, possess it as larvae. The basal joint 

 of the second pair of legs bears a broad file-like 

 area, and the third pair of legs is much reduced in 

 size and paw-like, with hard finger-like points 

 which scrape the file and so produce sounds. The 

 use of this power to the insect is unknown. The 

 most probable explanation we can suggest is, that 

 as the larvae feed in decaying wood, the sounds may 

 be useful in enabling them to avoid cutting across 

 each other in their boring operations. The grub 

 of our Stag Beetle {Luc anus cervus\ also a wood- 

 feeder, has a similar arrangement. 



Several other of our native beetles have stridu- 

 lating organs, among them Trox sabulosus, one of 

 the carrion-chafers. On the upper side of the 

 last ring but one of the hind body there are two 

 raised lines, and on the under side of the wing- 

 covers there are two file-like ribs. By movements 



