A horse fly lands on a steer at the Douglas County Fairgrounds. With a wet spring and a fairly wet summer, insects, including horse flies, are out in full force most places.

A horse fly lands on a steer Sunday at the Douglas County Fairgrounds. With a wet spring and a fairly wet summer, insects, including horse flies, are in full force most places.

If you have gone swimming recently, you may have noticed some unfriendly visitors.

Pools have become gathering places for a large, black insect known as the horse fly. Its habit of buzzing around humans and its painful bite can turn a relaxing day by the water into torture.

“They have been awful,” said Jennifer Clark, a South Park wading pool attendant. “They freak the kids out.”

Clark has been working at the wading pool for three summers, and this is the first that she has seen the flies. She said they gather in groups of at least four on the sides of the pool.

Fortunately, she hasn’t been bitten yet.

“The day I get bit will be the day I quit,” she said.

Zack Falin, collection manager for the entomology division of the Natural History Museum and Biodiversity Research Center on the Kansas University campus, has noticed more horse flies this year.

He’s swatted some away at the Lawrence Outdoor Aquatic Center, 727 Ky., where he takes his children, he said.

Insects in general are having a good year, Falin said. A mild winter and a lot of rain in the spring and early summer spurred the increase.

“Ants and termites are doing well,” he said. “People have been hearing about a lot of critters in people’s houses.”

The flies are attracted to water, movement, warmth and carbon dioxide, making the pool prime horse fly territory.

Falin said the larvae of horse flies live in swampy ground and hatch about once a year in the middle to late summer.

“It’s been pretty damp,” he said “They are loving it.”

The horse flies are a particularly pesky summer pest because their bites are distinctly painful.

“Horse flies are just nasty,” Falin said.

As a distant relative of the smaller blood sucker the mosquito, horse flies are “kind of new at the game,” Falin said. That game would be the bite-and-suck-before-we-get-swatted-at game, which the mosquitoes have accomplished. “They haven’t evolved to get good at this,” Falin said.

Mosquitoes’ mouth parts are thin and “can kind of inject into you without you even knowing,” he said.

“Horse flies’ mouth parts aren’t as highly specialized, so it’s like cutting into you with a butter knife.”

Bug repellent could help, Falin said. Waterproof bug repellent would be ideal.

To make matters worse, there is more than one species of the horse fly. There are six, Falin said.

“Any one species is only out during one period of the summer,” he said. “They kind of overlap.”