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Mysterious ‘slime’ on Maine beaches turns out to be dead insects, officials say

This is what Wells Beach looked like on Monday, June 7. The black "slime" on the sand turned out to be millions of dead bugs.
This is what Wells Beach looked like on Monday, June 7. The black "slime" on the sand turned out to be millions of dead bugs.John Lillibridge

If you visited Wells Beach in Maine recently, you may have noticed some dark goopy stuff on the sand. And if you happened to walk barefoot, your feet were probably stained black.

The mysterious substance caught the attention of many beachgoers in Wells, York, and Ogunquit over the weekend, leaving many wondering just what the slimy goop was.

State officials now have an answer, and it’s not pretty: dead insects.

Jim Britt, a spokesman for the Maine Department of Agriculture, Conservation and Forestry, said a Maine Forest Service entomologist is looking at a sample to determine the species of insect.

Britt said from what they know so far, it’s most likely a “harmless common kelp fly that feeds on decaying seaweed” and the black substance that’s been staining people’s feet is “the pigment that occurs naturally from what they eat.”

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Britt said the phenomenon first came to the attention of state officials over the weekend, and there are no suspected health issues associated with the insects coming in contact with people’s skin.

Linda Stathoplos and John Lillibridge are retired NOAA oceanographers who are married and live in Wells. They collected a sample of the black stuff and helped solve the mystery.

“We got wind of it Monday,” he said. “We went walking, and saw all this goop on the beach. Every wave would bring in more of this crud.”

Lillibridge described the substance as “ooze” or “slime.” It was dark brown in color, and “almost looked like tiny pieces of seaweed or algae,” he said. “If you walked through it, your feet would turn black.”

Lillibridge said his wife Linda put some of it under a microscope and learned the answer when she found herself looking at the bodies of tiny winged insects.

“It was not what we expected at all,” he said. “We were surprised it was bugs, and not tar or algae or some other thing.”

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“There must have been millions...millions of dead bugs. All these little bug carcasses,” Lillibridge said. “You can’t tell they’re bugs until they’re under a microscope.”

Retired oceanographer Linda Stathoplos collected a sample of the black material and looked at it under a microscope. It turned out to be dead insects. The tip of the sewing pin in this photo shows just how small they were.
Retired oceanographer Linda Stathoplos collected a sample of the black material and looked at it under a microscope. It turned out to be dead insects. The tip of the sewing pin in this photo shows just how small they were. Linda Stathoplos

Lillibridge said the black pigment poses no danger to humans, and the stains are not permanent. “Like henna dye, it wears away eventually. It’s just a natural dye. Like getting berry stains on your fingers,” he said.

Lillibridge and Stathoplos brought home samples that can be used for further examination. “We threw the slime in the fridge,” he said.

On Wednesday Lillibridge said the dead insects had already been washed away from Wells Beach.

“Now they’re gone,” he said.

Once the state confirms what kind of insects they are, local officials will be sharing what they learn with beachgoers.

The town of York’s Parks and Recreation Department posted a message on the top of the department’s webpage to let people know that officials were working on getting answers.

“The Parks and Recreation Department is working with our Healthy Maine Beaches Coordinator, from the Department of Environmental Protection, to determine what is causing the black stains on the feet of beachgoers,” the message reads. “We will be provided the most up to date information and will pass it along to you, once we have it.”

Britt said the insects may be identified by as early as Wednesday afternoon. He also commended Lillibridge and Stathoplos for their work.

“Bravo to John and Linda for digging in and helping solve this mystery,” Britt said.

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Emily Sweeney can be reached at emily.sweeney@globe.com. Follow her on Twitter @emilysweeney.