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parts of the body. In the insects the blood serves almost entirely to carry the food, and the oxygen is conveyed through the animal by a remarkable contrivance found only in the insects, the spiders, and a few related forms.

124. Respiratory system.-If we examine an insect, the grasshopper for example, we find a number of small brown spots on each side of the abdomen, each of which under a magnifying-glass is seen to be perforated by a narrow slit. Carefully opening the body, we find that each slit is in communication with a white, glistening tube that rapidly branches and penetrates to all parts of the animal. When the body is expanded the air rushes into the outer openings, on through the open tubes, and is distributed with great rapidity to all the tissues of the body. In many insects some of these tubes connect with air-sacs which probably serve to buoy up the insect during its flights through the air.

125. Wingless insects (Aptera).-The simplest of all insects are the fishmoths and springtails, relatively small organisms covered with shining scales or hairs. The first of these is occasionally seen running about in houses feeding upon cloth and other substances, while the latter live in damp places under stones and logs. They are without wings, but are able to run rapidly and to leap considerable distances. In addition to the ordinary appendages, the abdomen bears what are perhaps rudimentary legs, a fact which, together with their relatively simple structure, strengthens the belief that the insects have descended from centiped-like ancestors.

126. Grasshoppers, crickets, katydids, etc. (Orthoptera).— Rising higher in the scale of insect life, we arrive at the group of the cockroaches, crickets, grasshoppers, locusts, and other related insects. Four wings are present, the first pair thickened and overlapping the second thinner pair. The latter are folded lengthwise like a fan, which is said to have given the name Orthoptera (meaning straight-winged) to

this group of insects. These extend all over the world, being particularly abundant in the warmer countries, and their strong biting mouth-parts and voracious appetites render many of them dreaded pests to the farmer. The cockroaches are nocturnal in their habits, racing about at night, devouring victuals in the pantry and gnawing the bindings of books. During the day their flat bodies enable them to secrete themselves in crevices wherever there is sufficient moisture.

In the grasshoppers, locusts, katydids, and crickets the body is more cylindrical, and the hind pair of legs are often greatly lengthened for leaping.

FIG. 76.-The Rocky Mountain locust.-
After RILEY, from The Insect World.

The crickets and katydids are nocturnal, the former remaining by day in burrows which they construct in the earth, the latter resting quietly in the trees. At night they feast upon vegetable matter principally, though

some species are known to prey on small animals. Those insects we usually term grasshoppers (properly called locusts) are specially destructive to vegetation. Some species are strong fliers, and this, connected with their ability to multiply rapidly, renders them greatly dreaded pests. They have been described as flying in great swarms, forming black clouds, even hiding the sun as far as the eye. could reach. The noise made by their wings resembled the roar of a torrent, and when they settled upon the earth every vestige of leaf and delicate twig soon disappeared.

The eggs of the majority of Orthoptera are laid in the ground, where they frequently remain through the winter. When hatched the young quite closely resemble the parents, and, after a relatively slight metamorphosis, assume the adult form.

127. Dragon-flies, may-flies, white ants, etc.-The dragon-, caddis-, may-flies, ant lions, and the white ants possess four

thin and membranous wings incapable of being folded. These possess a network of delicate nervures, giving the general name nerve-winged insects to these various small orders. Of the forms mentioned above, all but the white ants lay their eggs in the water, and the developing larvæ

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spend their lives in this medium until the time comes for their complete metamorphosis into the adult. The larvae of the caddis-flies protect themselves within a tube of stones or sticks bound together with silken threads, which they usually attach to the under side of stones in running water. On the other hand, the young of the dragon- and may-flies, provided with strong jaws, are active in the search of food and very voracious. In time they emerge from their larval skin and the water in which they live, and after a life spent on the wing they deposit their eggs and perish. The adult ant-lion, a type of the related order (Neuroptera), which has somewhat the appearance of a small dragon-fly, lays its eggs in light sandy soil. In this the resulting larvæ excavate funnel-shaped pits, at the bottom of which they lie con

cealed. Insects stumbling into their pitfalls are pelted with sand, which the ant-lion throws at them with a jerky motion of the head, and are speedily tumbled down the shifting sides of the funnel to be seized and devoured.

While the white ants are not in any way related to the true ants, they possess many similar habits. Associated in great companies, they excavate winding galleries in old logs and stumps, and, further, are most interesting because of the division of labor among the various members. The wingless forms are divided into the workers, which excavate, care for the young, and otherwise labor for the good. of the others; and into the soldiers, huge-headed forms,

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FIG. 78.-Ant-lion larva plowing its way through the sand (upper figure) while another is commencing the excavation of a funnel-shaped pit similar to one on right. Photograph by A. L. MELANDER and C. T. BRUES.

whose strong jaws serve to protect the colony. The remaining winged forms are the kings and queens. In the spring many of the royalty fly away from home, shed their wings, unite in pairs, and set about to organize a colony. The queen rapidly commences to develop eggs, and in some

species her body becomes so enormously distended with these that she loses the power of locomotion and requires to be fed. A single queen has been known to lay eggs at the rate of sixty per minute (eighty thousand a day), and

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FIG. 79.-Termites or white ants. a, queen; b, winged male; c, worker; d, soldier. those destined to royal rank are so nursed that they advance farther in their development than the remaining sterile and wingless forms.

128. The bugs (Hemiptera).-The large and varied group of the bugs (Hemiptera) includes a number of semi-aquatic species, such as the water-boatmen, often seen rowing themselves along in the ponds by means of a pair of oarshaped legs, in search of other insects. Somewhat similar at first sight are the back-swimmers, with like rowing habits, but unique in swimming back downward. Both of these bugs frequently float at the surface, and when about to undertake a subaquatic journey they may be seen to imprison a bubble of air to take along. Closely related are the giant water-bugs (Fig. 80), which often fly from pond to pond at night. In such flights they are frequently

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