204 
HEMIPTERA. 
3. Bark-lice (Coccidad) ; having threadlike or tapering 
antenna;, longer than the head ; the males alone provided 
with wings, which lie horizontally on the top of the hack ; 
no beak in this sex ; females wingless, hut furnished with 
beaks ; the feet with only one joint, terminated by a single 
claw ; skins tolerably firm and hard ; two slender threads atl 
the extremity of the body , no piercer in the females. 
1. IIarvest-flieS. ( CicadadcB .) 
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- 
drams, 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 
