Imago

Definition

The sexually mature, adult stage of an insect, reached after completion of metamorphosis and the final ecdysis. In holometabolous insects, the imago emerges from the pupa; in hemimetabolous insects, it follows the last nymphal instar. The imago is typically the dispersive and reproductive phase, bearing fully developed wings in winged species (except in mayflies, where a winged subimago precedes the sexually mature imago).

Etymology

From Latin imago meaning 'image' or 'likeness', referring to the final, definitive form of the insect.

Example

In the monarch butterfly Danaus plexippus, the imago emerges from the chrysalis with soft, folded wings that expand and harden within hours; only at this stage does the insect possess functional reproductive organs and embark on long-distance migration.

Synonyms

• Adult
• imaginal stage

Related Terms

• subimago
• Teneral
• Ecdysis
• instar
• pupa
• nymph
• complete metamorphosis
• Incomplete metamorphosis
• life stage

Usage Notes

Contrasts with immature stages (larva, nymph, pupa). In mayflies (Ephemeroptera), the subimago—a winged but sexually immature stage—molts once more to reach the true imago, a unique exception among insects. The term is sometimes extended to other arthropods with distinct adult stages but is most precise in entomology. Not to be confused with taxonomic names containing 'Imago' (e.g., fossil genera Imagocnus, Imagotaria).