Animals Without Backbones
David Bunch
The animals that do not have backbones, the invertebrates, outnumber the vertebrates many times. There are at least ten times as many kinds of animals without backbones. The ones we see most often are the insects. Insects are so numerous that they are the largest single division of the animal world. They are the beetles, bees, ants, termites, grasshoppers, mantises, June bugs, flies, crickets, wasps and hornets, moths, butterflies, cockroaches, and countless others.
They run, jump, walk, fly, swim, and burrow through the earth. They eat many things-plants, live animals, and dead animals. Some are parasites and must live on other plants or animals. In many insects there is a change between birth and maturity, or growing-up, which is called metamorphosis. This includes two, and sometimes three, different stages, at which times the insect looks and acts as though it were not the same creature at all. When there is complete metamorphosis, with three stages, the insect first hatches from an egg, in the form of a little worm, or grub.
This is called the larval stage, and the little worm is called a larva. The larva eats and eats, and grows larger. Then it enters the pupal stage, at which time the insect sometimes spins a silky envelope, called a cocoon, all around itself. There it sleeps for a time, and then comes out, with wings and other changed features. There are several kinds of metamorphosis, with different kinds of stages, depending upon the insect.The group includes 95% of all animal species.
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