Swarm of mayflies ‘like a plague’ invade town

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A massive swarm of mayflies has invaded the town of Havana, Illinois, creating a slippery mess and several accidents.

Havana police tell NewsChannel 4 that it's unlike anything they've ever seen before. "We have mayflies but never an invasion like this," said Officer Stark.

The swarm has its sights set on a main bridge, which has prompted the Havana Police Department to send out this warning on its Facebook page: "At one point they had piled 6 inches high and when ran over, became very slick. There were already motorcycle accidents due to this and cars stuck in the center of the bridge."

Commenters say the swarm resembles "a plague."

Officer Stark says no one there knows why the swarm chose Havana, but the same thing happened last year over a different Illinois bridge, connecting the city of Savanna with Sabula, Iowa.

"The biggest thing I noticed was (mayflies) piled knee-high in front of their headlights from just sitting there," Reserve Officer Stephen Thayer of the Sabula Police Department told WQAD.

In that case, the Department of Transportation had to use a snow plow to remove the insects, then sand the bridge due to being so slippery from crushed mayflies.

Mayflies are aquatic insects that can hatch in enormous amounts at the exact same time from spring to fall, as female mayflies can lay up to 3,000 eggs each.

The swarms that Illinois has seen may have been due to the newly-hatched swarm being attracted to lights on the bridge above the water where they emerged.

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