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Butterflies and moths are easily mistaken for each other, but one distinction between them often appears during their pupal stage. When most butterfly caterpillars reach full size, they attach themselves to a leaf or other object and shed their skin a final time, forming a chrysalis, a hard, shell-like skin, which protects the pupa inside. The chrysalis may be dull and rough or shiny and smooth, usually blending into its surroundings. Most moth caterpillars, by contrast, create a cocoon to protect the pupa, rather than forming a chrysalis. The cocoons usually resemble hard silk pouches, but some moths also incorporate materials like hairs and twigs.