noun
adult insect; imago
Entomological term for the final, fully developed stage of an insect after metamorphosis. Contrasts with 幼虫 (larva) and 蛹 (pupa).
幼虫がさなぎになり、やがて成虫になった。
The larva became a pupa and eventually turned into an adult insect.
成虫の寿命は種類によって大きく異なる。
The lifespan of an adult insect varies greatly depending on the species.
Compound of 成 (sei, 'become, mature') and 虫 (chū, 'insect'), literally 'mature insect'.