What is the process by which a caterpillar transforms into a butterfly called?

The process by which a caterpillar transforms into a butterfly is called metamorphosis. Butterflies undergo complete metamorphosis, passing through four major stages: egg, larva, pupa, and adult.

The caterpillar is the larval stage. It spends most of this period eating and growing, shedding its external cuticle several times as it passes through developmental stages called instars. When fully grown, it stops feeding and forms a pupa, commonly called a chrysalis in butterflies.

Inside the chrysalis, larval tissues are extensively reorganized as the adult body develops. Wings, antennae, adult legs, and the proboscis take shape before the butterfly emerges. Hormones, including juvenile hormone and ecdysone, help coordinate growth, moulting, and the transition between stages.

Pupation is only one part of the process, not the complete answer. “Transformation” describes the idea in ordinary language, while metamorphosis is the established biological term. Evolution is different again: it refers to inherited changes in populations across generations, not one animal’s life-cycle change.