So many mayflies hatched at once near the Mississippi River earlier this week, that they were picked up on weather radar.

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.

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's around 2,500 species of the insect, with over 600 species in North America.

But they aren't around long, an adult Mayfly lives from few minutes to a few days. Their only purpose is to reproduce and they die soon afterwards.

Credit: NWS La Crosse via Twitter
They also showed up in Southeastern Iowa this week:

According to Bugfacts.com, Mayflies have been around since before dinosaurs even existed; over 350 million years!

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