Page:Insects - Their Ways and Means of Living.djvu/139

 AND MEANS OF LIVING

living things. Therefore, animals principally have de- veloped the power of movement; they have acquired grasp- ing organs of some sort, a mouth, and an alimentary canal for holding the food when once obtained. In the insects, the locomotory function is subserved by the legs and by the wings. Since all these organs, the three pairs of legs and the two pairs of wings, are carried by the thorax (Fig. 63, Th), this region of the body is distinctly the locomotor center of the insect. The legs (Fig. 64) are adapted, by modifications of structure in different species, for walking, running, leaping, digging, climbing, swim- ming, and for many varieties of each of these ways of pro- gression, fitting each species for its particular mode of living and of obtaining its food. The wings of insects are important accesslons to their locomotory equipment, since they greatly increase their means of getting about, and thereby extend their range of feeding. The legs, fur- thermore, are often modified in special ways to perform some function accessory to feeding. The honeybee, as is well known, has pollen-collecting brushes on its front legs (Fig. 65 B), and pollen-carrying baskets on its hind legs (A). The mantis, which captures other insects and eats them alive, bas its front legs made over into those efficient organs for grasping its prey and for holding the struggling victim which have already been described (Fig. 46). The principal organs by which insects obtain and ma- nipulate their food consist )f a set of appendages situated on the head in the neighborhood of the mouth, which, in their essential structure, are of the nature of the legs, for insects have no jaws comparable with those of vertebrate animais. The mouth appendages, or mouth parts as they are called, are very different in form in the various groups of insects that have different feeding habits, but in all cases they consist of the same fundamental pieces. Most important is a pair of jawlike appendages, known as the mandibles (Fig. 66 B, Md), placed at the sides of the mouth (A, Md), where they swing sidewise and close upon each other

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INSECTS