Insects

Insects are the largest group of arthropods. There are over 800,000 different types of insects. They are very adaptable, living almost everywhere in the world. Insects have an exoskeleton that covers the entire body. The body consists of the head, the thorax, and the abdomen.

The insect's head has a pair of antennae and a pair of compound eyes. Compound eyes differ from human eyes. Instead of a single lens for each eye, compound eyes have many lenses for each eye. For example, the fly has about 4,000 lenses in a single eye. These mulitple lenses provide insects with very good eyesight.

Extending from the thorax are legs that the insect uses for walking, swimming, jumping, or digging. There might also be wings for flying. The abdomen contains important organs, including the heart, the respiratory system, the digestive system, and the reproductive system.

The insect's hard exoskeleton cannot grow, making it difficult for the insect's body to grow in size. To allow their bodies to grow, many insects must molt, or shed their exoskeletons. To molt, the insect wriggles out of this old skin, and then a new, larger exoskeleton develops.