holometabolous insects pass through several larval stages, or instars, as they grow and develop. The larva must moult to pass from each larval stage. These stages may look very similar and differ mostly in size, or may differ in many characteristics including, behavior, color, hairs, and spines, and even number of legs. Differences between larval stages are especially pronounced in insects with hypermetamorphosis. The final larval stage in some insects is called a prepupa. Prepupae do not feed, and become inactive. It is not uncommon that larval tissue that is broken down during metamorphosis increase in size by cell enlargement, while cells and tissues that will turn into imago grows by an increase in numbers. Pupa To enter the third stage of homometabolous development, the larva undergoes metamorphosis into a pupa. The pupa is a quiescent, non-feeding developmental stage. Most pupae move very little, although the pupae of some species, such as mosquitoes, are mobile. In preparation for pupation, the larvae of many species seek protected sites or construct a protective cocoon of silk or other material, such as its own accumulated feces. Some insects undergo diapause as pupa. In this stage, the insect's physiology and functional structure, both internal and external, change drastically. Pupae can be classified into three types: obtect, exarate, and coarctate. Obtect pupae are compact, with the legs and other appendages enclosed, such as a butterfly chrysalis. Exarate pupae have their legs and other appendages free and extended. Coarctate pupae develop inside the larval skin. Imago The final stage of holometabolous insect development is the adult, or imago. Most adult insects have wings (excepting where secondarily lost) and functioning reproductive organs. Most adult insects grow very little after eclosion from the pupa. Some adult insects do not feed at all, and focus entirely on mating and reproduction. Some adult insects are postmitotic at adult emergence, with dividing cells restricted to specific organs. Cyrtodiopsis dalmanni is one such species, that does feed in the adult stage but does not grow in size. Nutrition is utilized in adults for growth of the internal reproductive structures. Evolutionary context of holometabolan development Around 45% to 60% of all known living species are holometabolan insects. Juveniles and adult forms of holometabolan insects often occupy different ecological niches, exploiting different resources. This fact is considered a key driver in the unusual evolutionary diversification of form and physiology within this group. According to