ORTHOPTEKA. 



117 



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

 furnished with ridges like those of a file (Fig. 133, /;). 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 

 b tn-rowers. 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 



FIG. 134 Gryllotalpa 

 SeriOUS peStS. borealls. 



II. The True Crickets. To this group belong our com- 

 mon, black acquaintances that peep at us from the cracks. 



