How insect metamorphosis works

Growth requires a series of molts

An insect's external skeleton does not expand continuously, so an immature insect passes through stages separated by molts. Each interval between molts is an instar. Wings, when present, become functional only in the adult in nearly all insects — mayflies are the exception, flying as a winged subimago before a final molt — though wing pads can become visible on later nymphs. Silverfish illustrate a less dramatic, ametabolous pattern: young resemble smaller adults, and adults can continue to molt. [1][3][4][6]

Complete metamorphosis separates four stages

Beetles, flies, butterflies and moths, ants, bees, and wasps are among the groups with egg, larva, pupa, and adult stages. Larvae primarily feed and grow; the pupa is the reorganizing stage from which the adult emerges. Larvae and adults may use different foods and habitats, so finding a caterpillar or grub is evidence of a life stage, not a miniature version of the adult. [1][2][3][4]

Incomplete metamorphosis has no pupa

Grasshoppers, true bugs, dragonflies, damselflies, and other groups develop from egg through nymphal stages to adult without a pupa. A grasshopper nymph broadly resembles a small wingless adult, while a dragonfly nymph is aquatic and looks substantially different from the flying adult. The shared feature is the gradual series of nymphal molts, not a promise that juvenile and adult live side by side. [1][2][3][5]

Find the transition without interfering

Look for feeding damage and larvae on host plants, shed exoskeletons on stems, aquatic nymphs visible from the bank, pupae fixed beneath leaves or structures, and newly emerged adults resting while their body and wings finish expanding. Record stage, date, host or substrate, and behavior. Do not peel a pupa, pull an emerging adult free, or move it for a cleaner photograph. [1][2][4][5]

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