Impending mayfly hatch causes southeastern Minnesota bridge to go dark
The lights will go out on a bridge over the Mississippi River in Winona, Minnesota, for the next few weeks to squelch the impact of a mayfly hatch.
The Minnesota Department of Transportation said the overhead lights on the Highway 43 bridges will be off until mayflies fully hatch, "to reduce the number of mayflies on the bridge."
Having mayflies on the bridge can "cause dangerous driving conditions because it becomes slippery," MnDOT said.
While the insects are harmless, their sometimes overwhelming numbers can make them a nuisance. Still, the Minnesota Department of Natural Resources said they are extremely important in the aquatic food web, and are fed upon by other invertebrates, amphibians, reptiles, fish, birds, and mammals.
Mayflies spend 99% of their lives as larvae living in the sediment of freshwater systems like the Mississippi River, the DNR said. The hatching phenomenon in the Mississippi River occurs as the burrowing mayflies emerge all at once to mate, lay eggs and then die.
In 2021, a massive hatch in downtown St. Paul blanketed the city's roads and sidewalks. A year later, a hatch near La Crosse, Wisconsin, was so large it showed up on radar.
