Insects are the largest group of arthropods. There are over 800,000 different types of insects. Insects are very adaptable, living almost everywhere in the world. Common insects include the fly, beetle, butterfly, moth, dragonfly, bee, wasp and praying mantis.

Insects have an exoskeleton that covers their entire body. An insect's body consists of 3 parts: the head,thorax and abdomen.

The insect's head has a pair of antennae, and a pair of compound eyes. Compound eyes are different from human eyes which have 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. This provides them with very good eyesight.
The thorax contains the legs for walking, swimming, jumping or digging. The thorax may also have wings for flying. The abdomen contains many body organs, such as the heart, respiratory system, digestive system and reproductive system.

The insect's hard, exoskeleton makes it difficult for the insect to grow and get larger. This is because the exoskeleton can't grow and get larger. Many insects must molt in order to grow. Molting is the process where an insect sheds it outer skeleton. It wriggles out of this old skin, and a new, larger exoskeleton develops.