wings of such an insect, while modifying the sound, by no means prevented it being made; and it is a fact also that no sound is produced by other insects whose wings vibrate with great energy.

89. The peculiar chirp of the cricket is made by the forewings being rubbed rapidly against the hind-wings upon which they rest; one of the large veins in the fore-wing being thickened and notched like a file, and the wing itself acting as a resonant body in augmenting the sound. The males, only, make this sound; the females are silent; and if the fore-wing of the female be examined, the vein in question is not thickened, nor is it rough, like a file.

Mr. Samuel H. Scudder has stated that the grasshoppers produce their sound, or stridulate, in four different ways: "1. By rubbing the base of one wing-cover upon the other, using for that purpose the veins running through the middle portion of the wing; 2. By a similar method, but using the veins of the inner part of the wing; 3. By rubbing the inner surface of the hind-legs against the outer surface of the wing-covers; and 4. By rubbing together the upper surface of the front edge of the wings and the under surface of the wing-covers. The insects which employ the fourth method stridulate during flight-the others while at rest. To the first group belong the crickets; to the second, the green or long-horned grasshoppers; to the third and fourth, certain kinds of short-horned or jumping grasshoppers."

90. Harris, in describing the third method of stridulation,

says that "their instruments may rather be likened to violins, their hind-legs being the bows, and the projecting edge of the wing-covers the strings," and adds that when a grasshopper begins to play "he bends the shank of one hind-leg beneath the thigh, where it is lodged in a furrow designed to receive it, and then draws the leg briskly up and down several times against the projecting lateral edge and veins of the wing-cover. He does not play both fiddles together, but alternately, for a little time, first upon one, and then on the other, standing meanwhile upon the four anterior legs and the hind-leg which is not employed."

FIG. 92.-Leg of a Grasshopper magnified, showing Ridge of Fine Teeth on the Inside of the Leg, marked a, by which the Insect rasps the Wing; b, c, Different Views of Ridge of Fine Teeth, highly magnified.

A figure is here given of the hind-leg of a common grasshopper, showing the row of minute teeth which occur on the inside of the leg, and which are drawn across the edge of the wing. The pupils may imitate the sound thus produced by drawing a coarse file, or the teeth of a comb, rapidly across the edge of a stiff sheet of paper.

CHAPTER XIII.

HABITS AND STRUCTURE OF INSECTS (CONTINUED).

91. A LITTLE bug, called the tree-hopper, has a peculiar history in its young state. The eggs of certain species are laid in the ground, and, as soon as these hatch, the young ones crawl up the stems of grass, and, piercing the grass with their mouth-parts, commence to suck the juices contained therein. While this action is going on, a clear, watery fluid escapes from certain pores in the body, and in a short time the young insect is completely immersed in it. As it is obliged to breathe air, it secures this by turning up the hinder part of the body, and by means of little appendages, clasping a bubble of air, which then flows along the under side of the abdomen; here it is taken in through the spiracles. The air having been so used, is allowed to escape in the fluid in which the insect is immersed. This operation is repeated over and over again, fresh bubbles of air being thus secured, and then escaping in the fluid. After a while the fluid becomes filled with these little bubbles, which soon convert it into a frothy substance, and this is the origin of the white flecks which occur so thickly on grass, and which is here commonly called frog-spit, and, in England, cuckoospittle.

92. There are certain insects belonging to the same group which are aquatic, and whose young come to the surface of

H

the water, and in the same manner secure air. So this little tree-hopper, while in the young state sucking the juices of grass, and completely immersed in a watery fluid, may be looked upon as an aquatic larva during this stage.

a

FIG. 93.-GRASS, WITH THE FROTH UPON IT, a, a, and a Young Insect exposed at b.

FIG. 94.-A PORTION OF A GRASS-STEM, WITH THE YOUNG INSECTS MAGNIFIED: a, the Insect reaching out the Hinder Part of the Body to secure a Bubble of Air; b, an Insect allowing a Bubble of Air to escape in the Fluid, the dotted line b indicates the bubble; c, the Mouth-parts, like a Sting, piercing the Grass.

Let the pupils collect and examine this froth, and, by carefully wiping it away, they may expose the young insect fastened to the grass.

93. The insect called the seventeen-year cicada, or seven

teen year locust as it is improperly called, has an interesting life-history.

The perfect insect is shown in Fig. 95. They may be known by the peculiar loud, buzzing sound emitted by the male. This sound can oftentimes be heard at a great dis

tance.

FIG. 95.-SEVENTEEN-YEAR CICADA.

The seventeen-year cicada is found rarely in Southern New England, but is common in the Southern and Western States. This species exists in great numbers, and does immense damage to the trees which it infests. The female deposits her eggs in the twigs and smaller branches of oaks. Little furrows are made in the twig, side by side, and into these furrows the eggs are laid. The leaves wither on the trees from the injuries inflicted in this way. Little insects hatch from the eggs, entirely different in appearance from the parent; and these, running to the end of the twig, fling themselves off, and falling to the ground dig their way down, till they come to some root upon which they fasten, and with a piercing sting suck the juices of the root. Here they remain for nearly seventeen years, slowly growing. At the end of that time they assume the