Mayfly

A very well camouflaged Mayfly.
Mayflies or shadflies are aquatic insects belonging to the order Ephemeroptera. Over 3,000 species of mayfly are known worldwide, grouped into over 400 genera in 42 families. Mayflies are relatively primitive insects and exhibit a number of ancestral traits that were probably present in the first flying insects, such as long tails and wings that do not fold flat over the abdomen. They are aquatic insects whose immature stages (called "naiads" or "nymphs") live in fresh water, where their presence indicates a clean, unpolluted environment. They are unique among insect orders in having a fully winged terrestrial adult stage, the subimago, which moults into a sexually mature adult, the imago.