How to deal with outdoor flies
Dump standing water: drill holes in old tires, clean your gutters, don't pile grass clippings, keep the trash can covered, dump and replace water in birdbaths and wading pools weekly.
Consider insect repellents—but read the label first.
Putting up traps? Site them away from homes—you don't want to attract flies to your spot.
Don't bother with bug zappers—flies ignore them. Besides, they often kill beneficial insects.
What they look like
Big or small, all flies have two wings. Most are beneficial, helping you with garden pests and pollinating flowers. The common pesky flies are: House flies—the same ones you find inside. Don't bite, but invite themselves to your picnic. Black flies or gnats—small, but big-time annoyances with painful bites. Stable flies—same size as a house fly but bite with a lance-like mouthpart sticking out in front of their head. Usually bite your legs. Horse flies—lots of kinds, but all are big and all bite. Circle before landing. Deer flies—dark blotches on clear wings. Attracted to a moving target—like you on your lawnmower. Mosquitoes—hear a high-pitched whine? These dainty flies are known worldwide for the trouble they cause.
Where they live
Many biting flies spend their youth in water. If your property is near a stream or swamp it will be prone to these pests. Horse, deer, and black flies hatch in flowing rivers or muddy shores, so getting at them isn't easy. But dealing with mosquito, stable, and house fly breeding sites is doable. Old tires, unused plant pots, buckets, tarps . . . all collect pools of rainwater mosquitoes lay eggs in. House and stable flies lay eggs in rotting stuff: manure piles, grass clippings, uncovered garbage.
What they do
Besides those painful or itchy bites, flies spread diseases. Planet-wide, the mosquito is the deadliest animal in the world.
TAMU's Mosquito Safari
EPA's Repellent Search
eXtension on mosquitoes
See results from the Northeastern IPM Center's resources database.