'One of those things living near the river': Mayflies will be swarming soon in York County

Tina Locurto
York Dispatch
Mayflies along the Susqhehanna River in Wrightsville, Saturday, July 13, 2019. Dawn J. Sagert photo

Mayflies will be out in full force in York County soon — which means lights out for the Veterans Memorial Bridge, waterfront properties and nearby shops on the Susquehanna River.

The tiny, aquatic insects will emerge from the riverbanks and congregate for a week in heavily lit areas to swarm, mate and die.

On the Veterans Memorial Bridge, which connects Wrightsville in York County to Columbia, Lancaster County, the lights are typically shut off to reduce the bug swarm for six to eight weeks starting in late June, said Dave Thompson, a spokesperson for the Pennsylvania Department of Transportation.

"Columbia borough takes the lead on turning off the lights and publishes something on their Facebook page before doing so," Thompson added via email.

The specific time at which mayflies emerge can be tricky to nail down, and relies heavily upon river conditions, temperature and the daylight cycle, said Geoffrey Smith, a Susquehanna River biologist.

Mayflies along the Susqhehanna River in Wrightsville, Saturday, July 13, 2019. Dawn J. Sagert photo

"Every tree, every bush — every physical thing is covered in them," Smith said. "It can't be stopped, but they're trying to work around it."

Public officials have been going dark to deal with the swarm in recent years, and those with private waterfront property along the Susquehanna River should consider following suit, he said. 

People riding bicycles or motorcycles should avoid traveling at night, Smith added.

"It's short-lived," he said. "It'll be a couple of days, and it's just one of those things living near the river."

— Reach Tina Locurto at tlocurto@yorkdispatch.com or on Twitter at @tina_locurto.

A swarm of mayflies hovers over the Route 462 bridge over the Susquehanna River late Saturday evening, June 13, 2015, between Columbia and Wrightsville, Pa. Authorities say the swarm was so dense that it caused a series of motorcycle crashes and prompted them to close the bridge. (Blaine Shahan/LNP via AP)