Mayfly

Mayfly

Mayfly

The Mayfly has three stages to its life; the naiad, dun and spinner. Naiads live primarily in streams under rocks, decaying vegetation, or in the sediment. They drift in the current. Few of the species live in lakes yet they are among the most prolific. The naiads have three tail filaments and seven pairs of abdominal gills. The naiad stage may last from several months to as long as several years, with a number of moults along the way.

They swim to the surface to hatch into a dun. Mayflies are unique among the winged insects in that they moult one more time after acquiring functional wings (this is also known as the alate stage); this second-to-last winged instar is usually very short, often a matter of hours, and is known as a dun to fly fishermen. This stage is a favorite food of many fish, and many fishing flies are modeled to resemble them.

The dun flies off the water and then moults, returning to the water as a spinner to mate and lay eggs. As an adult they have delicate veined wings held vertically at rest. The spinner dies on laying its eggs and drifts down the river. All these stages are fed on by trout. Mayflies hatch in the middle of the day during the cooler parts of the year and around dawn and dusk in warm weather.