Weather Radar Detects MASSIVE Mayfly Swarm

The mayflies are coming! And their swarms are so massive that they look like one big rainstorm on local weather radars.

The NOAA and the National Weather Service (NWS) have recently released radar imagery that picked up a massive echo as mayflies emerged from the Mississippi River and took to the air.

According to the NWS Weather Forecast Office, the event occurred last Sunday evening around 8:45 and produced an echo value "similar to that of light-moderate rain."

This 'storm' of flies reportedly reached as high as 2500 feet above the ground before dispersing to harass the residents of La Crosse, La Crescent, and Stoddard, who reported literal piles of the swarming insects. The swarm is being carried northward by winds over time, already having reached as far as Black River Falls.

Amazingly, this seemingly apocalyptic swarm is a yearly occurrence, and is an important part of the Upper Mississippi river's ecology.

"As nymphs, these aquatic insects proceed through one or two years of larval development as filter feeders, consuming decaying organic matter at the river bottom. In summer, large numbers of nymphs synchronously emerge from the water at dusk and take flight as sub adults," the US Fish and Wildlife Service (FWS) reports.

This swarming flight only lasts about 36 hours, with the sub adults becoming fully grown just long enough to mate before returning to the river to lay eggs and die.

Unlike the dreaded Mormon cricket infestation of the south-west, this makes the swarming mayflies less of a pestilent nightmare and more of an amusing - if somewhat disgusting - occurrence.

Large swarms like this one remind FWS mayfly watchers that the populations are doing well - a testament to the Mississippi River's good health as well.