HEMIPTERA. 165 



and wings frequently wanting in the females ; feet two-jointed ; 

 the body very soft, generally furnished with two little tubercles at 

 the end ; no piercer in the females. 



3. Bark-lice (Coccid^e) ; having ' threadlike or tapering an- 

 tenna?, 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. 



I. Harvest-flies. (Cicadadce.) 



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 eleva- 

 tion 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 instru- 

 ments 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 lo- 

 cust 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, covered with numerous 

 fine plaits, and, in the species above named, are lodged in cavi- 

 ties 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 are alternately 

 tightened and loosened, recovering their natural convexity by their 



