The insect stage that harbors these changes is the pupa, from the Latin word for doll. Apparently, ancient people saw in the insect form a likeness to the inanimate toy for a child. Insects protect their pupae in a variety of ways. Some, like the common housefly, are thrifty, using their last larval skin to form a protective cover for the pupae. Still others follow the Boy Scouts' lead and make a tent-like structure by tying the edges of leaves together.
Some insects spare no expense or trouble to make their cocoons.
Probably the most famous of this group is the silkworm, which spins a cocoon of silk for pupation. Centuries ago, it was discovered that the silken thread used by silkworm larvae to construct pupation chambers could be unwound and used for human purposes. Since that time, uncounted silkworms have spun up cocoons with the biological intent of becoming an adult. However, humans have interceded to claim the silk for their own uses. And then there are those insects that choose the no-frills method.