Dana Thiede

KARE-TV, Minneapolis-St. Paul, Minn.

TREMPEALEAU, Wis. — Residents along the Mississippi River would rather do without this rite of summer, the annual mayfly hatch that fills the air with insects and leaves surfaces of cars and just about everything else with a slimy mess.

A hatch starting at about 8:45 p.m. CT Sunday was so prolific that it created a bow echo on radar, similar to one that would be made in a significant rainstorm, according to the La Crosse, Wis., office of the National Weather Service. A weather service employee captured some images of the short-lived insects covering nearly everything in their path.

Mayfly larvae burrow into lake and river bottom mud until they mature. Then they swim to the water's surface and emerge as adults.

In the air they become a feast for frogs, birds, spiders and other insects. Weather forecasters say Sunday's hatch was the Hexagenia bilineata species, one of the larger varieties.

Typically, mayflies emerge in three or four hatches from June to August along the upper Mississippi, but water temperature plays a big role in when the larvae mature. The delay of warm weather in the spring may have contributed to Sunday's massive, simultaneous hatch.

Up and down the river, the mayfly hatch has been a problem. About 80 miles upriver from here, police in Trenton, Wis., say mayflies may have triggered a three-vehicle crash Sunday.

The road about 50 miles southeast of Minneapolis had become slick from the mayflies Sunday evening, causing at least one of the drivers involved in the crash to lose control of her vehicle. Visibility was limited at the time of the crash because to the massive cloud of mayflies in the air, police said.

Two people were injured but only one was taken to a local hospital.

The good news: The insect onslaught doesn't last long. The life of an adult mayfly lasts from a few hours to a few days, enough time to mate and start the cycle again.

Contributing: The Associated Press