How does a caterpillar form a cocoon or chrysalis before becoming an adult?

Caterpillars of the order Lepidoptera prepare for their transformation into adults by entering the pupa stage, though the method varies significantly between moths and butterflies.

Most moth larvae construct a cocoon for protection. These are often made of silk, sometimes incorporating materials like larval hairs, waste products, or chewed wood pulp. Silkworms, for instance, produce long, continuous protein filaments from specialized glands that harden upon contact with air. These cocoons may be hidden in soil, leaf litter, or attached to twigs.123

In contrast, most true butterflies do not spin cocoons. Instead, they pupate "naked," with their own hardened body forming the chrysalis. These are often secured to a surface using a silk pad and a stalk called a cremaster, or sometimes supported in an upright position by a threadlike silk girdle wrapped around the body. Once protected, the caterpillar undergoes a major internal rebuilding of tissues to emerge as a mature adult.1