All animals that have ears have ways of communicating by =sounds=. Why would it be impossible for the grasshopper to have a _voice_, even if it had vocal cords in its throat? The male grasshoppers of many species make a =chirping=, or stridulation, by rubbing the wing against the leg. Look on the inner side (why not outer side?) of the largest joint of the hind leg for a _row of small spines_ visible with the aid of a hand lens (Fig. 111). The sound is produced by the outer wings rubbing against the spines. Have you noticed whether the sound is produced while the insect is still or in motion? Why? The male grasshoppers of some species, instead of having spines, rub the under side of the front wing on the upper side of the hind wing. [Illustration: FIG. 111.—_A_, ROW OF SPINES, _z_, used in chirping. _B_, the same more enlarged. ] =Wings.=—To what is the first pair of wings attached? The second pair? Why are the wings not attached to the prothorax? Why are the wings attached so near the dorsal line of the body? Why are the second and third rings of the thorax more solidly joined than the first and second rings? [Illustration: FIG. 112.—GRASSHOPPER IN FLIGHT. ] Compare the first and second pairs of wings in shape, size, colour, thickness and use (Fig. 112). How are the second wings folded so as to go under the first wings? About how many folds in each? =Draw= a hind wing opened out. =Head.= What is the shape of the head viewed from the front, the side, and above? _Make sketches._ What can you say of the neck? Is the head movable in all directions? What is the position of the large =eyes=? Like the eyes of the crayfish, they are _compound, with many facets_. But the grasshopper has also _three simple eyes_, situated one in the middle of the forehead and one just above each antenna. They are too small to be seen without a hand lens. How does the grasshopper’s range of vision compare with that of the crayfish? [Illustration: FIG. 113. ] Are the =antennæ= flexible? What is their shape? Position? Are they segmented? Touch an antenna, a wing, a leg, and the abdomen in succession. Which seems to be the most sensitive to touch? The antennæ are for feeling. In some species of insects they also are organs of hearing and smelling. The =mouth parts= of a grasshopper should be compared with the mouth parts of a beetle shown in Fig. 113, since they correspond closely. If the grasshopper is fed with a blade of fresh grass, the function of each organ may be plainly seen. It is almost impossible to understand these functions by studying a dead specimen, but a fresh specimen is much better than a dry one. [Illustration: FIG. 114.—_a_, FOOD TUBE OF BEETLE. _b_, gizzard; _d_, intestine; _c_, biliary vessels. See Fig. 127. ]