Mayflies cover the side of a business in the the La Crosse, La Crescent, to Holmen Area (Wisconsin 2014)

Swarms of mayflies on the sides of a building at night, lit up by the green lights on the side of the building

Mayflies cover the side of a business in the the La Crosse, La Crescent, to Holmen Area (Wisconsin 2014) Credit: Tim Halbach