It may be hard to believe that a beautiful creature like a butterfly was once an ugly, wormlike creature like a caterpillar, but this is exactly how the colorful, graceful butterfly’s life cycle works.
There are four stages in a butterfly’s life. The process of going from one stage to another is called metamorphosis. The first stage begins when the female lays her eggs, usually on a plant which will provide food. Soon, a caterpillar, called a larva, begins to form inside each egg. After a few days, or a few months-depending on the variety of butterfly, the caterpillar is large enough to break out of the shell and continue growing outside. It begins by eating its shell, then goes on to eat the leaves of the plant on which its egg was laid.
The full-grown caterpillar gives off a thin stream of liquid from glands below its mouth. This liquid hardens into a silky thread which the caterpillar attaches to a twig or leaf. With this thread it spins a shell-like covering around its body. Inside the shell, the caterpillar changes into a pupa, or the body of a butterfly. This stage can take from ten days to several months.
When the pupa has grown into an adult butterfly, it gives off a fluid which softens the shell. Then it expands its body and cracks the shell. Within half an hour, the butterfly has pumped air into its body, its blood begins to circulate, and it is ready to fly away.
Many kinds of caterpillars deliberately eat plants which, although healthy to them, are poisonous to enemies who try to eat them!