Cocoon Cocoon is a protective covering that encloses the pupa and sometimes the larva of many insects. The mature larva prepares the cocoon as a shelter around itself. Inside the cocoon, the larva changes to a pupa and eventually transforms into an adult insect. Among the insects that spend part of their lives in cocoons are wasps, bees, caddis flies, moths, and some ants.
Many spiders spin silk cocoons around masses of their eggs and sometimes around their prey.
The chief substance of most cocoons is silk. But the larva often incorporates other substances, including soil, sand grains, plant materials, and hair or waste from its own body. Some cocoons contain very little silk at all. But many species pass the pupal stage in soil or in parts of plants without forming a cocoon. A few butterfly caterpillars make flimsy cocoons, but most pupate as a hard-shelled chrysalis.