Massive Mound of Dead Mayflies Found on Pennsylvania Bridge

A heaping pile of dead mayflies was spotted on a bridge in Columbia, Pennsylvania, on June 22, amid a notorious annual insect swarm.

This video, taken by Tom Johnson-Medland, shows the huge mound of mayflies that hatched overnight and died on the Veterans Memorial Bridge, which spans the Susquehanna River and connects Columbia to the town of Wrightsville. Johnson-Medland estimated that the largest pile was three-and-a-half-feet high at its highest point.

These tiny aquatic insects, which often emerge from the riverbanks to swarm, mate, and die, tend to live less than two days.

The bugs come out in full force during the spring and summer months in the area, with the Pennsylvania Department of Transportation typically shutting the lights off on the Veterans Memorial Bridge from May through late June to reduce the volume of mayfly hatches, according to local media.

“I walk the bridge every morning. This was the largest of three piles [I saw] on the bridge today,” Johnson-Medland told Storyful. Credit: Tom Johnson-Medland via Storyful