What is the purpose of the pupa?

Butterflies are insects that go through a process called complete metamorphosis. This means that they look completely different as babies than as adults and go through many moults to grow. Pupation is the most drastic change for an insect that goes through complete metamorphosis--it's the process where the animal takes a couple weeks to develop from caterpillars to butterflies. Without this stage, the larva could never grow up!