The egg is laid on the leaves of trees and other plants.
The egg hatches into a larva (caterpillar).
The caterpillar eats and eats.
It grows too big for its skin, the skin splits open.
The caterpillar sheds its old skin (molts).
The new skin is a different color each time the caterpillar molts.
The fourth time it molts the skin is green.
Then the caterpillar spins a long thread of silk and wraps itself up in the thread.
It is now a pupa. The case is called a cocoon.
(note: a butterfly case is called a chrysalis)
The pupa case is attached to trees or in cracks and stays there all winter.
The pupa is changing inside from a crawling insect to a flying insect.
When days get warmer, a moth (or butterfly) comes out. It spreads is wings to dry and then flies away.