pupa

A pupa is a life stage in the development of certain insects that undergo complete metamorphosis, occurring between the larval and adult (imago) stages. During this period, the immature organism is typically inactive and non-feeding while its tissues and organs are reorganized to form the mature insect’s structures. Pupation enables larval and adult forms to occupy different habitats and exploit different food sources, reducing direct competition between life stages.

There are two common forms of pupae. In many butterflies and moths, the chrysalis is a hardened, often colorful, protective case to which the developing adult is attached by silk or other structures. In many flies, the pupa is a puparium, a hardened covering formed from the larval skin that encloses the developing insect. Some other insects may pupate within a silken cocoon or within the remains of the larval skin.

During the pupal stage, cellular reorganization takes place as larval tissues are broken down and adult tissues and organs are formed. Hormonal signals, including ecdysone and juvenile hormone, regulate the timing and progression of metamorphosis. The duration of pupation varies by species and environmental conditions and may include diapause, a period of suspended development, to survive adverse conditions.

Emergence of the adult, called eclosion, ends the pupal stage. After eclosion, the insect expands and dries its wings (in winged species) and begins reproductive or dispersal activities. The pupal stage is characteristic of holometabolous insects such as butterflies, moths, beetles, bees, wasps, and flies.