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Why do many insects spend the winter in the pupal stage?

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Illustration showing a variety of adult insects, each labeled with its common name and order, including walkingstick, earwig, stonefly, tree cricket, dragonfly, female scale, cat flea, thrips, sucking louse, thysanuran, ant, scarab beetle, stinkbug, mosquito, and cabbage butterfly, highlighting their diverse shapes and sizes. — insect An illustration of insect diversity.

Many insects spend the winter in the pupal stage as a form of diapause, a period of arrested development and reduced metabolic activity used to survive unfavorable environmental conditions.12

While insects can enter this state at any stage of their life cycle, it occurs most commonly in pupae, particularly in temperate latitudes. The onset of this dormancy is typically triggered by a decrease in daylength as summer wanes, which signals the insect's endocrine system to cease the secretion of growth and molting hormones. Without these hormones, specifically ecdysone, development is halted until more favorable conditions return.21

During this time, the pupa remains protected within structures like cocoons or chrysalides, which may be hidden in soil, leaf litter, or attached to vegetation. This strategy allows the insect to remain in a state of developmental standstill, effectively waiting out the winter months before resuming metamorphosis into an adult when environmental stimuli become appropriate.231