Mayflies spend 99% of their lives in water and emerge as winged adults to take part in a mating swarm.

First came the flood, then the bugs — and the frogs.

It’s no wonder folks along the Missouri River to the south have been tossing around the word “plague.’’ As in the 10 plagues of Egypt.

“It does feel like that sometimes,’’ said Andrew Wagner, who works in Hamburg, Iowa.

Thankfully, no one has been struck down by boils, but there have been reports of bugs caking windshields so thick on stretches of road between Omaha and Kansas City that drivers have to pull over to clean up the mess.

They’ve sold out of windshield wiper fluid at Dominator Fuel in Rock Port, Missouri. Other gas stations report they’ve gone through twice the usual amount.

“The windshields are completely covered,’’ said Chandra McCarty, a cashier at Dominator.

The main culprit seems to be mayflies, although mosquito numbers also are high because of standing water.

Mayflies spend 99% of their lives in water and emerge as winged adults to take part in a mating swarm. Then they quickly die. But even in those few days of life, they’re a nuisance, especially in big numbers.

“Flooding brought those and stirred them up,’’ said Pam Frana, a membership specialist for the Nebraska City Tourism and Commerce Department. “They are atrocious. They are horrid.’’

Walk outside some days, Frana says, and you’re surrounded: “There are just swarms of them, which is not normal.’’

Although residents report seeing many more bugs than past years, urban entomologist Jody Green, an educator with the Lancaster County Extension Service, said mayfly hatches are actually a yearly event. Some swarms can be so big that they’ve been detected on Doppler weather radar.

“As an entomologist, I would relish seeing them, but I am sure it might even gross me out, too, if I couldn’t help but step and squish them,’’ Green said.

Mayflies may be an irritant to humans, but they’re a good source of food for fish and reptiles. The insects are drawn to light and have attracted company looking for a late-night feast.

As in frogs.

At the Rockport gas station, they’ve been seeing 30 to 40 a night. They sit in front of the doors, lured by the bugs.

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“They try to come up and come in,’’ McCarty said.

They’ve got frogs in Hamburg, too. Even spiders have decided to join in on the feeding frenzy.

But there is a light at the end of the tunnel.

“It used to be so bad people couldn’t see when they were driving,’’ Wagner said. “It’s getting a lot better since the flooding is going down.’’