There are four stages in the life cycle of a butterfly or moth. They are the egg, caterpillar, pupa and adult. The caterpillar eats large amounts of food. Caterpillars even eat their own eggshells when they hatch. As the caterpillar feeds, it grows rapidly. It sheds its skin periodically and grows a new larger one to help it increase in size.

Many insects have a life cycle similar to a moth or butterfly but the young stage may be called a grub or maggot. Larva is the word to describe the young stage of all insects with this kind of life cycle. So the caterpillar can also be described as the larva of the butterfly or moth.