METAMORPHOSIS

Metamorphosis usually proceeds in distinct stages, starting with larva or nymph, optionally passing through pupa, and ending as adult. There are two main types of metamorphosis in insects, complete and incomplete.


In incomplete metamorphosis, the development of larva often proceeds in repeated stages of growth and ecdysis, these stages are called instars. The juvenile forms closely resemble adults, but are smaller and, if the adult has wings, the juveniles lack wings. The differences between juveniles in different instars are small, often just differences in body proportions and the number of segment.





In complete metamorphosis, the larvae differ markedly from the adults. Insect which undergo complete metamorphosis pass throught a larval stage, then enter an inactive state called pupa, and finally emerge as adults. Inside the pupa, the insect will excrete digestive juices, to destroy much of the larva's body, leaving a few cells intact. The remaining cells will begin the growth of the adult, using the nutrients from the broken down larva.