Mary Allen
Insects are small animals. They belong to the arthropods. They are therefore closely related to millipedes, crabs, and arachnids. It is believed that there are about a million different species of insects. They live all over the world, just not in the sea.
From the human point of view, many insects are harmful. For example, they eat plants that are grown in agriculture. Or they transmit diseases such as malaria. But other insects eat the harmful insects. For example, ladybugs feed on aphids. Honey bees are insects that humans even keep getting honey from them. They are also important for pollinating fruit trees.
How is the body of insects structured?
An insect’s body has three parts, also called limbs. The middle one is the chest, and on it are three pairs of legs. So insects have six legs, unlike spiders, which have eight legs. On the breast part are also the wings of the insects. The other two parts of the insect’s body are the head and abdomen.
Insects have blood. It fills a large sac in which the internal organs float. At the back of this “blood sack” is a continuation with a simple heart that contracts and relaxes rhythmically. The most important artery is the aorta, which leads to the head in the brain. The legs, wings, and abdomen are also supplied with blood in this way.
Insects don’t have lungs. Tiny canals lead from the surface of the body into the interior, which is called tracheae. They branch out like the branches of a tree. This gets oxygen into the body. Insects cannot actively breathe in and out. The air is only moved by the wind or by the flapping of the wings of other insects.
Insects have a foregut, a midgut, and a hindgut for digestion. The foregut consists of the mouth and esophagus. In the midgut, food is digested and the usable parts are absorbed by the body. The rest of the food is prepared in the rectum and excreted as feces.
Insects reproduce in much the same way as birds do. They also have sex organs very similar to those of birds or mammals. They mate, then the female lays her eggs. An egg becomes a larva. This then becomes the adult animal. The larvae of butterflies are also called caterpillars. She first turns into a “doll” from which the adult animal then slips.