204 HEMIPTERA. 



3. Bark-lice (Coccidje) ; having threadlike or tapering 

 antennje, longer than the head; the males alone provided 

 with wings, which lie horizontally on the top of the back ; 

 no beak 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. (Oicadadts.) 



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 description 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 im- 

 properly 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 

 relax, which they do with great rapidity, the drum-heads 



