Metamorphosis is the process that an insect undertakes to pass from one stage, usually a larva or nymph stage, to an adult stage. Insects that go through some type of metamorphosis will usually go through four stages in their life cycles. They are: Egg, Larva, Pupa and Adult.
Metamorphosis stages vary from species to species but all relatively follow this pattern. Some develop more slowly than others as in beetles (slow developers ) and ladybugs (fast developers).
Most larva will feed very heavily in their current stage, gaining weight and growing in size. Most often, the larval stage is when the insect will weigh MORE than an adult of the same species. Upon maturity, the voracious appetite once present is no longer, allowing the insect to pursue it's daily work life.
Insects have varying degrees of defense when in the more vulnerable stages. Larva taste bad to unsuspecting predators, by hiding away in trees and crevices or by becoming difficult to swallow when attacked.
Metamorphosis will usually involve the insect finding a safe place to rest, developing a hard casement or cocoon on the outside of it's shell, and developing a soft adult insect on the inside. Once the process is complete, the shell or casement breaks open revealing the adult form of the insect. The insect is then ready to reproduce. Before doing so, the insect must take in air or water to 'fill out' the new body, and must survive long enough to have it's new 'skin' become hard and develop into an exoskeleton for protection.