'We had 6 inches of dead mayflies': Millions of bugs invade Wisconsin gas station

NEKOOSA, Wis. -- Mayflies invaded a gas station in Nekoosa, Wisconsin. It's an annual invasion, but this year they decided to focus on a gas station.

They piled on top of each other on the pumps and the store, WSAW reported.

Mountains of mayflies consumed the BP, covering gas pumps and the outside of the store Wednesday night.

The lights attracted them, as thousands piled on top each other.

"On the window sills alone we had 6 inches of dead mayflies," one employee said.

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BP workers said they spooked many customers away from stopping to get gas.

"I was doing the leaf blowing, and they were gonna get gas; they would look, and their car windows would be down a little bit because it was hot out. They would roll them up and be like this (nods head)," store manager Jasmine Stebnitz said.

It took the employees over four hours to clean them up.

They had to use leaf blowers to get them off the pumps and shovel them into garbage bags.

"We have to struggle to get it over to the garbage because they're so heavy," Stebnitz said.

The BP is across the street from the Wisconsin River, so it gets the brunt of the bugs.

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Jamee Hubbard is a professor of biology at UW-Stevens Point.

She said this year there were fewer parasites in the water to eat the mayflies and keep the population down.

Water quality is another reason there were so many.

"If our water quality goes down, like pollution for example, then we will start to see the populations decline simply because of negative changes in water quality. So Mayflies also serve as a really good indicator of the health of our streams and rivers and some lakes," Hubbard said.

Once they come out of the lake, they mate and migrate over to light, where they live for 24 to 48 hours before dying and causing a mess like this one.