Mayflies (also known as shadflies or fishflies in Canada and the upper Midwestern U.S.; also up-winged flies  in the United Kingdom) are aquatic insects belonging to the order Ephemeroptera. This order is part of an ancient group of insects termed the palaeoptera, which also contains dragonflies  and damselfies. Over 3,000 species of mayfly are known worldwide, grouped into over 400 genera in 42 families

Mayfly