Closely allied to the bugs is a group of remarkable insects to which naturalists now apply the name of Cicada, but which are generally, though improperly, designated Locust by the common people. They are readily distinguished by their broad heads, large prominent eyes, with three eyelets triangularly placed between them, and delicately transparent, veined wing-covers and wings. The abdomen is short and pointed, and the legs are short, the anterior femora being much thickened and toothed beneath. The hinder extremity of the body of the female is conical, and the under-side has a longitudinal channel for the reception of the ovipositor, or piercer, which is furthermore protected by four short-grooved pieces which are immovably fixed to the sides of the channel. The piercer itself consists of two outer parts grooved on the inside and slightly enlarged and angular at the tips, which are externally beset with small saw-like teeth, and a central spear-pointed borer which plays between the other two, thus combining the advantages of an awl and a double-edged saw, or rather of two key-hole saws cutting opposite to each other. A hard, horny substance, called chitine, the same as exists in the stings of bees and wasps, is the material of its composition. It would be impossible to conceive of anything more exactly fitted for its required uses than is this beautiful complicated instrument. But the most peculiar characteristic of this family, however, consists in the structure of the mechanism by which the males make the trilling sound for which they have been so long famous. In the male of the Seventeen-year Cicada the musical instrument consists of two stretched membranes, one on each side of the body, which are plainly to be seen immediately behind the wings. These membranes are gathered into numerous fine plaits, and are played upon by muscles or cords fastened to their under surfaces. When these muscles contract and relax, which they do with great rapidity, the drum-heads, which the membranes resemble, are alternately tightened and loosened, the effect of this alternate tension and relaxation being the production of a rattling sound very much like that caused by a succession of quick pressures upon a slightly complex and elastic piece of tin-plate. Certain cavities within the body of the insect, which may be seen on raising two large valves beneath the abdomen, and which are separated from each other by thin transparent partitions of the brilliancy of mica or highly polished glass, tend to increase the intensity of the sound.