All insects go through a series of changes as they mature (called metamorphosis) unlike mammals, where the young are born as ‘miniature’ adults.
With moths and butterflies, the first stage is the ovum or egg, the second stage the larva (larval stage) or caterpillar, the third stage the pupa (pupal stage) and finally it becomes the imago or adult, usually termed the ‘butterfly’ or ‘moth’. Moth caterpillars spin a silk cocoon around themselves to enter the pupal stage.
Most butterfly larvae, however, split open and then the inside forms a transparent skin or cuticle . This is called a chrysalis. (Just to complicate things… there are a few butterflies that spin a cocoon, but most make a chrysalis.)
