A cocoon is a casing spun of silk by caterpillars and certain other insect larvae. Butterfly caterpillars do not spin a cocoon but a chrysalis. Some caterpillars attach small twigs, fecal pellets or pieces of vegetation to the outside of their cocoon in an attempt to disguise it from predators. Others spin their cocoon in a concealed location - on the underside of a leaf, in a crevice , or down near the base of a treetrunk .

Silkworm cocoons are processed and used to produce natural silk for clothing.