Prepupation

Prepupation is a developmental stage in the life cycle of many holometabolous insects that occurs after the final larval instar and before pupation. During this stage the larva typically stops feeding, becomes quiescent, and may move to a site suitable for pupation. In some groups, the transition to a prepupal form involves a new molt; in others, the larva passes from the last instar directly toward the pupal phase.

Physiological and behavioral changes during prepupation reflect preparation for metamorphosis. Feeding ceases, metabolic processes reorganize, and the insect locates or constructs a pupal environment. In certain taxa, most notably many flies (Diptera), the prepupal larva forms a protective casing called a puparium, within which the true pupa develops. In other groups, such as some Lepidoptera, the transition to the pupal stage occurs as part of the final larval molt or within a chrysalis or cocoon, without a distinct external puparium.

Timing and duration of prepupation vary widely among species and are influenced by temperature, humidity, photoperiod, and food availability. Warmer conditions and abundant resources generally shorten the prepupal period, while cooler conditions can extend it or induce diapause.

The concept is important for understanding insect development and ecology, and has practical applications in pest management and biological research, where knowledge of prepupal timing can affect monitoring and control strategies.