What is the difference between a mayfly subimago and an imago?
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mayfly
An adult mayfly (Ephemera vulgata) in Europe.
The mayfly is unique among insects because it is the only group that continues to molt after developing functional wings. The transition between the nymphal stage and the final adult form involves two distinct winged stages:1
- Subimago (or dun): This is the first winged stage to emerge from the nymphal skin. The subimago is capable of flight, allowing it to move from the water to a sheltered resting place. Physically, it is softer and duller in color than the adult, with generally opaque, often mottled wings and shorter legs and tails.1
- Imago (or spinner): After an interval ranging from a few minutes to several days, the subimago sheds its exoskeleton one final time to become the imago. This is the sexually mature adult stage. Compared to the subimago, the imago is more vibrant, possesses clearer wings, and has longer legs and tails.1
It is a common misconception to view these two stages as different species, when they are simply successive developmental phases of the same insect.1