Complete metamorphosis. Computer illustration showing the process of complete metamorphosis (Holometabolism) in a butterfly. Complete metamorphosis is a form of insect development whereby the insect passes through four distinct life stages: embryo or egg, larva, pupa and adult (imago). In butterflies and moths (order Lepidoptera) the eggs (bottom) hatch into a caterpillar (larva, left), which then pupates (top) before hatching into the fully-formed winged adult (right).