ORTHOPTERA. 



117 



cover be examined with a microscope, it will be seen to be 

 furnished with ridges like those of a file (Fig. 133, b). On 

 the inner margin of the wing-cover, a short distance toward 

 the base from the end of the principal vein, there is a 

 hardened portion which may be called the scraper. This is 

 shown enlarged at c in the figure. Each wing-cover is there- 

 fore provided with a file and a scraper. When the cricket 

 wishes to make his call, he elevates his wing-covers at an 

 angle of about forty-five degrees with the body ; then hold- 

 ing them in such a position that the scraper of one rests 

 upon the file of the other, he moves the wing-covers back 

 and forth sidewise so that the file and the scraper rasp upon 

 each other. This throws the wing-covers into vibration, 

 and produces the call. 



There are comparatively few species of crickets, but they 

 represent three quite distinct groups. These can be dis- 

 tinguished as the Mole Crickets, the True Crickets, and the 

 Tree Crickets. 



I. The Mole Crickets. — These are 

 called Mole Crickets because they burrow 

 in the ground like moles. There are 

 species belonging to the next group, the 

 true crickets, which burrow in the ground ; 

 but the mole-crickets are pre-eminently 

 burrowers. The form of the body is 

 suited to this mode of life. The front 

 tibiae, especially, are fitted for digging; 

 they are greatly broadened, and shaped 

 somewhat like hands, or the feet of a 

 mole. Figure 134 represents one of 

 these insects. The mole-crickets feed 

 upon the tender roots of various plants, 

 and where they are common they are 

 serious pests. 



II. The Trtie Crickets. — To this group belong our com- 

 mon, black acquaintances that peep at us from the cracks 



FlG. 134 — Gryllotalpa 

 borealis. 



