The annual Mississippi river mayfly hatch was so intense this year that it created a bow echo on weather radar.
The hatch started at 8:45 p.m. CT on Sunday, USA Today reported. Mayfly larva burrow into lake and river bottoms until it is time for them to swim to the surface and swarm through the air.
These pesky insects tend to emerge in three of four hatches between the months of June and August. A delay in warm weather in the Mississippi region could be to blame for the massive hatch.
The swarm got so bad it triggered a three-vehicle crash on Sunday. The mayflies had causes a road southeast of Minneapolis to become slippery, leading a driver to lose control of her vehicle. The mayflies also impaired visibility at the time. Two people were injured but only one was taken to the hospital.
"They're sometimes accumulating in areas that are lit up at night; so street signs, any of the power poles that have power lights on them, those are objects that these animals will be attracted to," Harvey Halvorsen of the Wisconsin Department of Natural Resouces told WEAU. "Especially the bridges, if bridges have lighting, the Hexagenia adults will be attracted to the bridges."
The bugs live for only 48 hours and do not bite people, but can still be an extreme nuisance.
Glen Siewer, owner Mr. Sippi, located on the Wisconsin Channel of the Mississippi River, has already collected four wheelbarrows full of the pests.
"A lot of people don't like walking through them. The bridge up here gets extremely slippery. We have a couple of accidents just about every year due to the mayflies," Siewer told WEAU.
While being potentially dangerous, the mayflies do provide food for a number of local birds, fish, and frogs.
"They're highly sought after by birds," Halvorsen said. "They like to use that for food resources."
WATCH:
