These forms may be considered the musicians of the insect world. None of the insects can produce vocal sounds, that is, they have no voice, but they have certain appliances which enable them to produce sounds which can be heard a long distance. On hot days in summer is heard the constant and shrill zee-zeeing of the locust, while countless varieties lend their aid in producing a volume of sound. [Illustration: FIG. 195.--A grasshopper.] The "instruments" in the locust are (Fig. 196) minute teeth, arranged along the thighs; these are rubbed against the fore wings, producing the remarkable sounds. The locusts are commonly called grasshoppers. They have two pairs of net-veined wings, and hind legs adapted for leaping, by which they send themselves sprawling through the air, almost invariably using this method of escape instead of unfolding their delicate wings. All are mimics. The common ground locust resembles the dusty road and the dried foliage which it affects. Others, which live on plants, are a vivid green. Some which I find in my garden resemble closely the tender shoots of the passion vine, upon which they feed. [Illustration: FIG. 196.--Musical instruments of the locust: _a_, leg; _b_, _c_, teeth, enlarged.] The locusts (Acridiidæ) have short antennæ, large glassy eyes, and ears at the base of the abdomen. The female is provided with an appliance called the ovipositor, four sharp points with which the grasshopper digs holes in the ground; later these are used as a guide or funnel for introducing the eggs into the burrow. The mouth is supplied with parts adapted to biting. When a grasshopper (Fig. 195) is caught it exudes a peculiar fluid resembling molasses, a secretion of the salivary glands. The eggs are deposited in masses from sixty to one hundred. The young resemble the parent, but at first have no wings. The grasshopper in making its metamorphosis, or change from one stage to another, casts its skin in a manner calling to mind the crabs; in a word, it molts several times (Fig. 197). In accomplishing this, it often climbs a spear of grass and there shuffles out of its old skin and jumps away, leaving the hollow skin clinging to the grass. [Illustration: FIG. 197.--A grasshopper and young at different stages: _A_, larva; _B_, pupa; _C_, adult.]