COLUMBIA, Pa. (WHTM) – A swarm of mayflies caused several crashes and a bridge closure between York and Lancaster counties over the weekend.

The bridge closed Saturday night after mayflies swarmed the Route 462 bridge over the Susquehanna River and caused three motorcycle crashes. The bridge reopened Sunday morning, but closed again in the evening after another crash.

Now, piles of dead mayflies line the bridge. They smell like dead fish. It’s such a bizarre sight, Trevor Koch stopped to take pictures.

“This is wild to say the least,” Koch said. “This is pretty cool.”

It wasn’t so cool for bicyclists who had to navigate through the piles of dead bugs.

Tim Abbey with Penn State Ag Extension said there was a hatch.

“They are attracted to lights and with those being the brightest lights around on the river, that’s where they went,” Abbey said.

Abbey said that happens elsewhere, too, but mayflies have only swarmed the bridge during the past two years, ever since new lights were installed. They are bright and low, almost at street level, which why visibility was so bad.

“I don’t think it was something you could have guessed would happen,” PennDOT spokeswoman Fritzi Schreffler said. “Last year when it happened, I think everyone was taken aback when it first happened.”

What is the solution to this buggy issue?

“Turn the lights off for a week or so and they’re not going to be up there in the numbers that they are,” suggested Abbey.

That is easier said than done.

“For the road portion of it, we have the responsibility at PennDOT, but when it comes to the lighting that’s on the bridge, that it the responsibility of the local municipality,” Schreffler said. “They had approached us about putting these kinds of lights on the bridge. They were willing to pay for it.”

ABC 27 News contacted officials in Columbia, Wrightsville and West Hempfield Township. No one returned our calls. PennDOT officials said they are all meeting soon to find a solution.

Abbey said the worst of the swarm is over, but there may be minor swarms for a few days. Schreffler said drivers should be alert.