A thick, massive band of mayflies traveling along the Mississippi River created a swarm so intense it became visible on National Weather Service radars on July 20, 2014.
Communities in the Upper Midwest experience this alarming phenomenon nearly every year. Mayflies are insects with short life spans that typically emerge in the summer. Typically found near areas of fresh water, the insects hatch in large quantities.
La Crosse, located along the Mississippi River, makes for a prime mayfly habitat. In addition, the northern part of the Mississippi River has more moderate temperatures, creating conditions favorable to the insects.
After hatching, the bugs began latching onto almost anything on Sunday night, blanketing buildings, cars and gas pumps.
As the bugs mobbed areas across Wisconsin and Minnesota, visibility became poor and slimy roads made for dangerous driving.
According to the Minneapolis Star Tribune, the pesky insects were the root of a Wisconsin car accident.
One woman was hospitalized late Sunday evening after her car was struck by a vehicle that lost control after slipping on the bug-covered roads.