The mayfly lives for years underwater, but its final act lasts only a day.

Nature · Published 29 September 2026 Swipe more like this →

In short: Most of a mayfly's life is spent as an aquatic nymph, hidden beneath the surface for up to two years. Once it finally takes flight, it undergoes a rare transformation, shedding its skin even after growing wings. This fleeting adult stage is dedicated entirely to mating before the insect dies.

Mayflies, belonging to the order Ephemeroptera, are ancient insects that spend the vast majority of their existence as aquatic nymphs. During this immature phase, which can last from two weeks to two years, they live in freshwater environments, often burrowing into silt or clinging to rocks. These nymphs are vital to local food webs, acting as key players in the transfer of energy within their ecosystems. However, their presence is sensitive to environmental quality, as they require clean, oxygenated water to thrive. Recent studies have highlighted significant population declines, with some burrowing species dropping by over 50 percent due to pollution and habitat disruption.

The transition to adulthood is unique in the insect world. When a nymph is fully developed, it emerges from the water as a subimago, a winged but sexually immature form. After a period ranging from minutes to days, it molts one final time to become a fully mature imago. This makes mayflies the only insects known to shed their exoskeleton after they have already developed functional wings. In this final stage, the insects possess no working mouthparts or digestive tracts, meaning they are physically incapable of feeding.

Because they cannot eat, the adult mayfly's existence is brief, often lasting only a few hours. During this time, they gather in massive swarms to perform mating dances over water. These emergences can be so dense that they appear on weather radar and create hazards on roads. Once mating and egg deposition are complete, the adults die, leaving behind the next generation of eggs to settle at the bottom of the water, ensuring the cycle continues despite the brevity of their winged lives.

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