178 INSECTS INJURIOUS TO VEGETATION. 



in this sex; females wingless, but furnished with beaks; the 

 feet with only one joint, terminated by a single claw; skins 

 tolerably firm and hard ; two slender threads at the extremity 

 of the body ; no piercer in the females. 



1, Harvest-flies. ( Cicadadcs.) 

 The most remarkable insects in this group are those to 

 which naturalists now apply the name of Cicada. They are 

 readily distinguished by their broad heads, the large and very 

 convex eyes on each side, and the three eyelets on the crown; 

 by the transparent and veined wing-covers and wings ; and by 

 the elevation on the back part of the thorax in the form of 

 the letter X. The males have a peculiar organization which 

 enables them to emit an excessively loud buzzing kind of 

 sound, which, in some species, may be heard at the distance 

 of a mile; and the females are furnished with a curiously 

 contrived piercer, for perforating the limbs of trees, in which 

 they place their eggs. Without attempting a detailed descrip- 

 tion of the complicated mechanism of these parts, which could 

 only be made intelligible by means of figures, I shall merely 

 give a brief and general account of them, which may suffice 

 for the present occasion. The musical instruments of the 

 male consist of a pair of kettle-drums, one on each side of 

 the body, and these, in the seventeen-year Cicada (or locust as 

 it is generally but improperly called in America), are plainly 

 to be seen just behind the wings. These drums are formed of 

 convex pieces of parchment, gathered into numerous fine plaits, 

 and, in the species above named, are lodged in cavities on the 

 sides of the body behind the thorax. They are not played 

 upon with sticks, but by muscles or cords fastened to the 

 inside of the drums. When these muscles contract and re- 

 lax, which they do with great rapidity, the drum-heads are 

 alternately tightened and loosened, recovering their natural 

 convexity by their own elasticity. The effect of this rapid 

 alternate tension and relaxation is the production of a rattling 

 sound, like that caused by a succession of quick pressures 

 upon a slightly convex and elastic piece of tin plate. Certain 

 cavities within the body of the insect, which may be seen on 



