Sex-crazed Lesser flies will drive anyone crazy.

Those unlucky enough to walk into a swarm of them use their hands and arms to keep the pests from flying into their eyes, noses and ears as they hurry to get away.

Lesser flies, smaller than common house flies but no less annoying, congregate beneath tree branches, porch ceilings and deck overhangs. They're looking for females.

"The males are the antagonists," said Bill Todaro, a medical entomologist for the Allegheny County Health Department. "They form mating swarms and slowly circle in a cloud. They're frequently found in filtered light. They're a real nuisance."

Mr. Todaro said Lesser flies flourish in the spring, early summer and late fall. He said they usually hit their peak populations in July.

The appearance of the flies has been a recurring problem for homeowners who live near the Eichner family farm in McCandless, especially those living on Forest Edge Court, whose condos overlook the 15-acre farm.

They use fly strips, bait bags suspended from tree branches and spray cans of pesticide on the patio to combat the pests.

Although some neighbors don't think the Eichners are doing enough to eradicate the flies, the family disagrees.

"If there's anything more we can do, we will do it," said Dick Eichner, who operates the farm with his wife, Vi, and son Ron. They sell eggs and a variety of vegetables, and also operate a greenhouse.

The Eichners use a synthetic pesticide to spray the walls, ceiling and beneath the roof of a screened-in coop that houses 1,500 chickens. They use exhaust fans to vent the coop and fans to dry the chicken manure.

The manure is the problem. Lesser fly larvae breed in it. Females deposit eggs on the surface of the manure and the larvae hatch within two days. Maggots develop within 10 days. A new generation of flies emerge and the life cycle is repeated. Adults can survive for up to two months.

Patty and John Gross, whose home is across the road from the condo development, said the flies were so bad this summer that they covered the ceiling of their front porch.

"We had to be careful every time we opened the front door to keep them from getting in the house," Mrs. Gross said. "It's really disheartening. I found flies in some towels that I had in the dryer."

Kathy Kaiser, who lives down the street from the Grosses, said her family wasn't able to use its in-ground pool earlier this summer. "It was ridiculous," she said. "It's much better now. I hope they don't return this fall. Whatever [the Eichners] are doing, I hope they keep on doing it."

Dick Eichner said he would.

"We're doing the best we can, but our neighbors knew our farm was here when they moved here. In fact, the farm has been here since my grandfather started it in 1897."

Although state law requires that anyone planning to buy or build a home next to a farm receive a written notice about what that entails from the seller, some buyers may not pay any attention to it or fully understand what it means.

To make sure the owners of six new condos now being built above the farm are fully aware of the law, Mr. Eichner said he would erect a large sign facing the development. The last sentence of the sign, taken verbatim from the law, will read:

"This notice is to inform prospective residents that agricultural activities may generate dust, noise, odor and vibration or seasonal insect population."

Buyers be aware.

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