The mayflies visit Wisconsin annually, but not like this. Millions of them took over a Nekoosa gas station this week. They piled on top of each other on the pumps and the store. One store employee said they were six inches thick on the windows, likely attracted by the bright lights of the business at night. Many customers were afraid to use the pumps. One nightside employee said she watched at least six vehicles pull in the parking lot, then right back out without buying gas. One expert, Jamee Hubbard, a biology professor at U-W-Stevens Point, says the number of mayflies is larger than normal because there weren’t enough parasites to each them when they emerged from the water.