In fact, caterpillars don't form a chrysalis around themselves; it's already inside them! Caterpillars shed their skins (molt) about five times as they grow between hatching and pupation. Each time, a new, larger skin is ready underneath the old one, and the caterpillar grows until that skin is too small, then molts again. The sixth time, the new "skin" is the chrysalis. The caterpillar undergoes this molt hanging by its rear prolegs from a silken strand attached to a silken mat that it has woven on the underside of a leaf. It hangs for about a day before shedding its last caterpillar skin and emerging as a chrysalis (pupa). At first, the chrysalis is very soft but it quickly hardens to form a protective shell inside which the animal goes through the even more amazing transformation into a buttefly.