What makes an insect an insect are six legs, jointed bodies and an exoskeleton. Insects are cold blooded, and lay eggs. They have no lungs but breathe through spiracles found in their sides.
The body of an insect is divided into the head, the thorax and the abdomen. The head contains the insect's mouth parts, eyes and antennae. The thorax holds the legs and the muscles used in locomotion. The abdomen holds the digestive and reproductive organs.
The exoskeleton is made out of a tough material made of chitin. To grow, the insect must shed this exoskeleton or moult from time to time.