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save that it has no wings, these growing gradually as the creature increases in age. Fig. 87 represents a young grasshopper with the wings just appearing. At intervals, the insect sheds its skin, or moults, the wings continually increasing in length until mature size is reached.

Let the pupils endeavor to collect some young grasshoppers representing various stages of growth, and place these in their collections beside the full-grown one.

By searching in the grass, the cast-off skins of grasshoppers may be occasionally found still clinging to the spears of grass, where they were left when the grasshoppers shed them.

FIG. 88.-CAST-OFF SKIN OF A GRASSHOPPER.-The grasshopper has shed its skin while

clinging to a blade of grass. The skin is imperfect, the antennæ and parts of its legs are broken; the abdomen is shriveled, and does not show.

Fig. 88 shows the appearance of one of these cast-off skins. 85. Grasshoppers are often infested with parasites. Frequently the grasshoppers, in a sickly condition, are met with clinging to the grass, or bushes. A careful examination of them will show a number of little bright-red mites crawling on them, or attached near the base of the wings, and evidently the cause of their weakness.

Curious cases have been found wherein these creatures had met with fatal accidents. In their headlong fall to the

FIG. 89.-GRASSHOPPER PIERCED WITH SPEAR OF GRASS.

ground, after one of their reckless jumps, they are liable to have their armor pierced with the dried spears of grass. Fig. 89 represents a grasshopper which had been pierced in this

way, the dried point of the grass probably striking the head, and then glancing off, and entering between the head and the thorax.

86. In studying the early stages of the mosquito, it was found that at the outset the animal breathed air through an opening in the hinder part of the body; that soon after this the opening closed, and air was taken in by two openings on the back, but in no case did the insect breathe through its mouth. In the perfect insect, as well as in most larvæ, there are little openings along the sides of the body. These little openings communicate with tubes which branch, and subdivide again and again, sending their little air-twigs into every part of the body, even into the legs and the veins of the wings. These little tubes represent the lungs of an insect. They necessarily render the body very light besides.

w t

m s h

FIG. 90.-INSECT SHOWING THE SPIRACLES.-Grasshopper with the wings and two hinder pairs of legs removed to show spiracles, or openings in the sides of the body which communicate with the air-tubes within the body: w, showing where the wings were attached; h and m, where hind and middle legs were attached; s, spiracle on thorax; t, tympanum.

In large insects like the grasshopper the minute openings in the sides of the body can be plainly seen without the aid of a glass. The segments of the abdomen have each a little

opening, which is represented in the figure; and where the abdomen joins the thorax, a cavity lined with a delicate skin will be found, which is called the tympanum, and is supposed to be an organ of hearing. If the softer parts within the body of an insect be removed and slightly compressed between two pieces of thin glass, the air-tubes, looking like fine white threads, may be seen with an ordinary pocket-lens.

The air-tubes are called trachea, and the openings on the outside of the body which communicate with them are called spiracles.

87. Insects breathe by dilating and contracting the abdominal segments. The act of breathing can be plainly seen in the grasshopper or the honey-bee, and it will be noticed that after violent exercise, as in a long flight, the insect breathes more rapidly than when it has been at rest for some time, just as a boy after running finds himself compelled to breathe rapidly for a while.

After violent exercise the insect gets tired and rests. Bees may often be seen, after a long flight, to alight in the grass near a flower, and for a while appear so fatigued that they cannot reach the flower, but remain breathing very rapidly. Insects have curious ways of resting and sleeping. A species of wasp has been observed soundly sleeping while holding on to a blade of grass by its jaws alone, the fore-legs just touching the grass, while the body and the middle and hinder pair of legs were hanging downward, and not bearing against the grass at all, as shown in Fig. 91.

88. In this connection it may be well to allude briefly to

the manner in which the various sounds emitted by insects are made. It is obvious that the vibration of the wings produces the loud buzzing sound made by certain insects. But there are other sounds which are traced directly to the effect of the air rushing in and out of the spiracles, and impinging on certain plates whose sharp edges border the spiracle. The experiment has been made of closing the

FIG. 91.--WASP SLEEPING WHILE HOLDING ON TO A BLADE OF GRASS WITH ITS JAWS.

spiracles with varnish, when all noise ceased. It is believed that the mosquito produces its remarkable tones in this way. Such noises have always been associated with the vibration of the wings, because the noise seems to be made when the insect is flying, but the cause of this is explained by supposing that the violent muscular action of moving the wings also causes the air to be violently thrown out of the spiracles, and as a proof of this it has been found that cutting off the

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