MAY FLY

                                                                                                                    

         MAY FLY

                                                                                                                                                                                                                                                                    Mayflies or shadflies are insects belonging to the order Ephemeroptera (from the Greekephemeros = "short-lived" (literally "lasting a day" "daily" or "day-long"), and πτερόν, pteron = "wing", referring to the brief lifespan of adults). They have been placed into an ancient group of insects termed the Palaeoptera, which also contains dragonflies and damselflies. They are aquatic insects whose immature stage (called "naiad" or, colloquially, "nymph") usually lasts one year in fresh water. The adults are short-lived, from a few minutes to a few days, depending on the species. About 2,500 species are known worldwide, including about 630 species in North America.The naiads live primarily in streams under rocks, decaying vegetation, or in the sediment. Few species live in lakes, but they are among the most prolific. For example, the emergence of one species of Hexagenia was recorded on Doppler weather radar along the shores of Lake Erie.

Most species feed on algae or diatoms, but a few species are predatory. The naiad stage may last from several months to several years, with a number of moults along the way. Most mayfly naiads are distinctive in having seven pairs of gills on the dorsum of the abdomen. In addition, most possess three long cerci or tails at the end of their bodies. Some species, notably in the genus Epeorus, have only two tails. In the last aquatic stage, dark wingpads are visible. Developmentally, these insects are considered hemimetabolous. A more casual and familiar term is "incomplete metamorphosis". Mayflies are unique among insects in that they moult one more time after acquiring functional wings (this is also known as the alate stage); this last-but-one winged instar usually lives a very short time, often a matter of hours, and is known as a subimago or to fly fishermen as a dun. Mayflies in this stage are a favourite food of many fish, and many fishing flies are modelled to resemble them.