Wildlife Watching Wednesday: The Swarming Mayfly

By: Tom Berg

Mayflies are a common sight during the springtime and early summer, especially if you are near a source of water like a lake, river or creek.  Mayfly nymphs live underwater for anywhere from several months to a few years, depending on species and water conditions.  The nymphs eventually hatch out of the water and tend to swarm in huge numbers, living only a day or two as adults – just long enough to mate and for the females to deposit their eggs in the water to complete another generation.

There are more than 3,000 species of mayfly in the world, with more than 600 species living right here in North America.  Mayflies are insects, of course, and they are also called fishflies since they hatch out of the water where fish are present.  Some people call them willowflies since they are often seen clinging to willow trees along the shores of rivers, lakes and other bodies of water.

Adult mayflies have one or two pairs of wings, and at rest the wings are held upright and together.  A person can easily pick up a mayfly by the wings without harming it to examine it and then release it and let it fly away.  They also have extremely long tails and large compound eyes.  Mayflies can be a variety of colors, but brown, tan, yellow, white and black are some of the most common colors.

Although some people consider mayflies to be a nuisance since they tend to form large swarms and can cover almost every local surface near their hatching sites, mayflies are actually very beneficial creatures.  They are “bio-indicators”, meaning they are very sensitive to water pollution and provide an important indication of good water quality where they live.

Mayflies also perform an important role in their local ecosystem by serving as a source of food for other creatures.  Fish eat them in mass quantities since the mayfly nymphs live in the water, and birds gorge on them after they emerge from the water.  Frogs, toads and even other insects (like dragonflies) eat them, too. The winged adult mayflies are completely harmless to people, so pick one up and get a closer look the next time you see one!

Have you had a great outdoor experience? Join Global Outdoors and write a review to tell everyone about it! We’re building the home for trusted reviews of outdoor experiences, outfitters, and guides.