Any of various fragile winged insects of the order Ephemeroptera that develop from aquatic nymphs and live in the adult stage no longer than a few days. Varying in body length, mayflies have three slender tails, and their antennae are short and bristle like. Their nymphal gills are external, attached at the outer edge of the upper surface of the abdomen. Mayflies are the only insects that shed their skin after developing functional wings. These wings are almost always four in number, the front pair much larger than the hind pair, although a few species have no hind wings. The dun (or subimago), which emerges from the nymph, constitutes the true "hatch" of the angler. In the dun stage the wings are usually cloudy, often appearing pale blue, slate, olive, yellow, or white, sometimes with dark mottling. Mayflies occupy almost every type of freshwater habitat.
