hemimetabolic

Hemimetabolic, or hemimetabolous, refers to a pattern of insect development characterized by incomplete metamorphosis. In these species, the life cycle typically proceeds through egg, juvenile stages known as nymphs or naiads, and adult, with no pupal stage. Nymphs resemble small versions of the adult and molt several times as they grow, gradually acquiring adult size and features such as wings when present.

Development in hemimetabolous insects involves gradual transformation rather than a dramatic larva–pupa–adult progression. The immature forms often share a similar body plan with the adults, though they may differ in size, coloration, or the presence of wings and reproductive organs. In aquatic lineages, nymphs are usually aquatic and have adaptations for life underwater, while wing development, if it occurs, happens across successive molts.

Groups that exhibit hemimetabolism include many orders of insects. Common examples are the true bugs (Hemiptera, such as cicadas, aphids, and planthoppers), Orthoptera (grasshoppers, crickets, katydids), Mantodea (mantises), Blattodea (cockroaches and termites), Dermaptera (earwigs), Plecoptera (stoneflies), Phasmatodea (stick insects), and aquatic orders such as Ephemeroptera (mayflies) and Odonata (dragonflies and damselflies). The term is often contrasted with holometabolism (complete metamorphosis), in which insects have distinct larval and pupal stages that look very different from the adult. The word derives from Greek roots meaning “half” and “metamorphosis,” reflecting the partial transformation from juvenile to adult.