You may be wondering, what's the difference between a chrysalis and a cocoon? While the words may be used interchangeably, they actually are two different things!
A chrysalis is a hard outer shell that protects the butterfly pupa as it develops. A chrysalis may look very still, but there is a lot going on inside! The chrysalis stage is an important step where the caterpillar metamorphoses into a butterfly. The vast majority of butterfly species form chrysalides and do not form cocoons.
A cocoon is made of silk and is spun by some species of moths during their pupal stage. A few moth species go through metamorphosis in underground chambers.
While they may use different methods, butterflies and moths go through a similar metamorphosis while inside their chrysalis or cocoon.