subimago

The subimago is a stage in the life cycle of certain insects, most notably mayflies, that occurs between the nymphal and adult (imago) stages. This stage is characterized by the insect having developed functional wings and being capable of flight, but it is not yet fully mature. After a brief period, the subimago undergoes one final molt to become the adult imago. This is a unique characteristic of mayflies, as they are the only insects that molt after developing wings. The subimago typically appears duller and softer than the adult, with less developed wings and shorter legs and tails.12