Thousands of mayflies have taken over a bridge in Havana, central Illinois on June 27, 2016.
At one point the mound of insects piled 6 inches high.
The Havana Police Department warned drivers of a massive mayfly swarm on its Facebook page Monday morning, posting two photos that showed the bridge over the Illinois River and a local squad car blanketed by the bugs.
Newly winged mayflies will emerge from the waters where they live until adulthood in droves when triggered by the right temperature.
The insects then die within a few days.
The City of Havana Street Department and IDOT are working to get the mayflies under control.