  thumb|pupa of a mosquito a pupa (latin pupa for doll, pl: pupae or pupas) is the life stage of some insects undergoing transformation. the pupal stage is found only in holometabolous insects, those that undergo a complete metamorphosis, going through four life stages: embryo, larva, pupa and imago. (for a list of such insects see holometabolism). 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. ==position in life cycle== in the life of an insect the pupal stage follows the larval stage and precedes adulthood (imago). it is during the time of pupation that the adult structures of the insect are formed while the larval structures are broken down. pupae are inactive, and usually sessile (not able to move about). they have a hard protective coating and often use camouflage to evade potential predators. ===duration=== pupation may last weeks, months or even years. for example it is two weeks in monarch butterflies. the pupa may enter dormancy or diapause until the appropriate season for the adult insect. in temperate climates pupae usually stay dormant during winter, while in the tropics pupae usually do so during the dry season. anise swallowtails sometimes emerge after years as a chrysalis. ===emergence===  insects emerge (eclose) from pupae by splitting the pupal case, and the whole process of pupation is controlled by the insect's hormones. most butterflies emerge in the morning. in mosquitoes the emergence is in the evening or night. in fleas the process is triggered by vibrations that indicate the possible presence of a suitable host. prior to emergence, the adult inside the pupal exoskeleton is termed "pharate". once the pharate adult has eclosed from the pupa, the empty pupal exoskeleton is called an "exuvium" (or exuvia); in most hymenopterans (ants, bees and wasps) the exuvium is so thin and membranous that it becomes "crumpled" as it is shed. newly emerged females of the edith's checkerspot butterfly mate immediately with males, usually within less than an hour after
Developmental_biology Entomology