Common Name: Mayfly
Scientific Name: Ephemeroptera spp
Status: Important component of the food chain
Beneficial Stage: Immature and adult

Biology: Mayfly adults and immatures (nymphs or naiads) are one of the most common insects in fresh water ecosystems. Adults have two large membranous wings with extensive wing venation throughout that are held upright, like a butterfly, when at rest. The second pair of wings is reduced or lacking. Legs are long and the body is roughly cylindrical, bearing two very long, filamentous tails (cerci) at the end. Adults are very short-lived and may only be present a couple of hours to days but the immature stages may last a year or more.

Eggs of the mayfly are laid on the surface of lakes or streams, and sink to the bottom. Safter hatching, the nymphs may molt 20 to 30 times over a period of a few months up to year, depending on the species. Nymphs live primarily in streams under rocks or in decaying vegetation. Mayfly nymphs are distinctive in that most have seven pairs of gills on the abdomen. In addition, most possess three long tails at the end of their bodies.

Mayflies are unique among the winged insects in that they molt one more time after acquiring functional wings. This stage is usually very short, sometimes only a few hours. Mayflies are very common in the water and when a 'hatch' is on, the number of adults that congregate on the shorelines, near structures and even towns nearby can be simply staggering.

Value: Mayfly nymphs feed on algae, which is beneficial to other inhabitants of lakes and streams. However, even more importantly, mayflies are a vital part of the aquatic food chain, and are food to many fish and other insects.

Fly fishermen know to look for mayfly emergences as times when fish will be attracted to specific 'flies' and will adjust their fishing techniques accordingly.

Mayfly nymphs also are used as a 'bio-indicator' of water quality. Because they are very sensitive to changes in the water, their presence or absence in a given body of water may be used to rate how polluted the water may be.