Pupal transformation

A pupa (Latin: pupa for doll, plural: pupae) is the life stage of some insects undergoing transformation between immature and mature stages. The pupal stage is found only in holometabolous insects, those that undergo a complete metamorphosis, with four life stages: egg, larva, pupa and imago. The processes of entering and completing the pupal stage are controlled by the insect's hormones, especially juvenile hormone, prothoracicotropic hormone, and ecdysone.

The pupae of different groups of insects have different names such as chrysalis for the pupae of butterflies and tumbler for those of the mosquito family. Pupae may further be enclosed in other structures such as cocoons, nests or shells.

The pupal stage follows the larval stage and precedes adulthood (imago) in insects with complete metamorphosis. The pupa is a non-feeding, usually sessile stage. It is during pupation that the adult structures of the insect are formed while the larval structures are broken down. The adult structures grow from imaginal discs.

Pupation may last weeks, months or even years. This depends on temperature and the species of insect. For example, pupation lasts eight to fifteen days in monarch butterflies. The pupa may enter dormancy or diapause until the appropriate season to emerge as an adult insect. In temperate climates pupae usually stay dormant during winter, while in the tropics pupae usually do so during the dry season.

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