Stages of Butterfly Metamorphosis
Ross E. Hutchins
Butterflies and moths are among the insects that pass through four stages of development in their life cycles.
The first stage is the egg. Adult females lay eggs on the kind of plant their young will later need as food.
The eggs hatch into wormlike creatures known as larvae. The common name for the larvae of butterflies and moths is caterpillar. Caterpillars are busy and hungry. They may eat once or twice their own weight in leaves each day. After several days of such constant feeding, caterpillars outgrow their own skins. When this happens they molt, splitting the skin and crawling out of it. Caterpillars may shed their skins four or five times in this second stage of the life cycle.
In the third stage the caterpillar goes into a resting state and is called a pupa. Different caterpillars pupate in different ways. For example, many moth caterpillars burrow into the ground; others hide behind loose bark or in hollow logs. Some caterpillars rest in silken cocoons, which they make by spinning thread from their mouths. (Silk cloth is made from the threads in the cocoon of the silkworm moth.) The pupa does nothing except rest. This stage may last two weeks; it may last a whole winter. During this period the caterpillar changes into a full-grown butterfly or moth.
In its new and adult form, the butterfly or moth emerges wet and shaky from the cocoon. As blood flows into the veins of the wings the adult flutters and dries them. In a few hours, when the wings are strong and dry, the butterfly or moth flies off to live out its fourth, or adult, stage.
Photo © Ralph Clevenger/Corbis