Metamorphosis

A dramatic change in body form an animal undergoes between one life stage and the next, most familiar in insects and amphibians. Complete metamorphosis, the pattern the monarch butterfly follows, passes through four sharply distinct stages, egg, larva, pupa and adult, with the larval and adult forms so different in shape, diet and habitat that they function almost as two separate animals sharing one genome; a monarch caterpillar spends its larval stage eating milkweed leaves, then forms a chrysalis in which its body is almost entirely broken down and rebuilt before it emerges as a nectar-feeding, flying adult. Incomplete metamorphosis, the pattern used by grasshoppers and dragonflies among others, instead passes through a series of nymph stages that already resemble small, wingless versions of the adult, growing gradually rather than being rebuilt.