[L. insectus, cut into.] In point of number and variety of species by far the largest class of animals. The body, made up of a number of rings or segments, is divided into three parts - the head, forming one ring; the thorax, with three divisions ; and the abdomen, with eleven rings. The head has two jointed feelers, called antennae, which are used in smelling and as organs of touch and guidance, and three pairs of mouth appendages. The first pair, called mandibles, is used for cutting the food. Next come the first pair of maxillae, and below these the second pair of maxillae. Insects feed on different kinds of food, some living on animal and some on vegetable substances, while others suck juices. Hence arises a difference in the shape of their mouths - some being formed for biting and chewing, some only for sucking, and some for both. Three pairs of legs grow on the thorax, one pair on each ring; and they have usually either two or four wings also on the chest. The majority of insects are hatched from eggs, and these vary in number according to the kind of insect. Some kinds of insects, such as the hive-bee, the silk-moth, the cochineal and lac-insects, are very useful to man, other kinds, such as the locust, the grasshopper, the potato-bug, and many flies, are very harmful, destroying herbage and crops.
FIGURE SHOWING THE PARTS OP INSECTS.
head: bed,thorax; e abdomen; ff, antennae or feelers; gg 11, wings; iih h k k legs.