How does a caterpillar turn into a moth or butterfly?
The amazing set of transitions that Lepidoptera (and many other insects) undergo during their life cycle is called metamorphosis. Butterflies and moths are among the insects that go through four distinct phases of life: the fertilized egg and embryo, the caterpillar, the pupa (sometimes within a cocoon), and the adult. The transition that most captures our attention is actually two changes: from caterpillar to pupa and then from pupa to adult. After hatching from the egg, the caterpillar, of course, starts eating. Like any insect, the skeleton (exoskeleton or cuticle) is on the outside, so to grow the caterpillar must molt or shed its skin several times. Every time it sheds, the caterpillar will suck in air to enlarge the new soft cuticle before it hardens. The caterpillar, in other words, must pass through several instars, or different size stages, before it reaches the pupal stage. Also like any insect, the caterpillar has several segments. The segments are covered by a pretty tough
