INSECT METAMORPHOSIS
connected with its transformation, is subservient to the function of procuring food. Most species feed on plants and live in the open (Fig. 135 A); but some tunnel into the leaves (B), into the fruit (D), or into the stem or wood (C). Other species feed on seeds, stored grain, and cereal preparations. The caterpillars of the clothes moths, however, feed on animal wool, and a few other caterpillars are carnivorous.
The whole structure of the caterpillar (Fig. 136) betokens its gluttonous habits. Its short legs (L, ?AbL) keep it in close contact with the food material; its long, thick, wormlike body accommodates an ample food storage and gives space for a large stomach for digestive purposes; its hard-walled head supports a pair of strong jaws (Md), and since the caterpillar has small use for eves or antennae, these organs are but little developed. The muscle system of the caterpillar presents a wonderful exhibition of complexity in anatomical structure, and gives the soft body of the insect the power of turning and twisting in every conceivable manner. In contrast to the caterpillar, the moth or the butterfly feeds but little, and its food consists of liquids, mostly the nectar of flowers, which is rich in sugars and high in energy-giving properties but contains little or-none of the tissue-building proteins.
When we examine the young of other insects that differ markedly from the parent form, we discover the same thing about them, namely, the general adaptation of their body form and of their habits to the function of eating. Not all, however, differ as widely from the parent as does the caterpillar from the moth. The young of some beetles, for example (Fig. 137), more closely resemble the adults except for the lack of wings. Most of the adult beetles, too, are voracious feeders, and are perhaps not outdone in food consumption by the young. But here another advantage of the double life is demonstrated, for usually the grub and the adult beetle have different modes of life and live in quite different kinds of
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