A huge swarm of mayflies were captured on the radar at the National Weather Service on Sunday night as they emerged from the Mississippi River. They were seen to drift north in what looked like a yellow patch which slowly turned to blue dots till they dispersed. The radar appeared as if a thunderstorm or a heavy rainfall was covering the screen. The flies emerged in humungous numbers from the Mississippi river and enveloped roads as if a huge blanket was stretched across the roads.
These mayflies are attracted by lights and when they are crushed, liquid is release in the eggs which make roads slick and slimy. A car crash was reported in Wisconsin when the driver lost control and crashed into another car before striking a van.