For those of us living near bodies of water, the warmer weather means it’s time for the annual swarm of Mayflies. They begin hatching in May and continue to do so throughout spring and summer. I saw my first one of the season on Friday morning in Waterloo, two blocks away from the Cedar River:


According to, Mayflies have been around since before dinosaurs even existed; 300 - 350 million years ago. They are the oldest group of winged insects.

Even though they can be a nuisance around street lights and can make the road slick with their carcasses, a large Mayfly (or sometimes called a 'fishfly') hatch is a good indication of a healthy waterway -- they can only survive in 'clean' water. There are around 2,500 species of the insect, with over 600 species in North America.

Last June, the radar for the National Weather Service in La Crosse, Wisconsin, showed a mass appear over the Mississippi River on the Minnesota-Wisconsin border into Iowa in Allamakee County.

But they aren't around long, an adult Mayfly lives from few minutes to a few days. Adult mayflies don’t have time to eat, so they never develop functional mouths, which also means that they can’t bite you. (They also don’t have stingers) Their only purpose is to reproduce and they die soon afterward. But in their short lifespan, they are BUSY. The average female mayfly lays anywhere from 400 to 3,000 eggs.

But, the cleanup after mass death isn't a lot of fun. As seen in this video from 2018:

So, get your shovels ready. It's MAYFLY SEASON!


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