Backyard compost piles can be a source of stable flies, and you really don't want that. Stable flies look a lot like houseflies but have one important difference. They bite.
About the size of a housefly but with dark, irregular spots on its abdomen, stable flies have biting mouthparts through which they suck blood. The mouthpart, or proboscis, protrudes bayonet-like in front of its head.
In the South, stable flies may breed all year, but they're mainly pests in the spring and fall. The female lives about a week and lays 100 to 400 eggs during her lifetime.
The larva is a typical whitish maggot. The pupal case is chestnut brown and about a quarter-inch long. The complete life cycle of a stable fly can take 14 to 24 days from egg to adult during warm weather.
The female fly deposits eggs in spoiled or fermenting plant matter, such as decomposing grass clippings or hay. Larvae feed on this rotting organic material, then pupate nearby. Adult flies emerge several days later.
It's important, then, to make sure you're composting properly. Otherwise, you could be helping supply the neighborhood with bloodsucking flies.
Both male and female stable flies feed on blood, which they get by piercing a host's skin with their syringe-like mouthparts. They stay on the animal long enough to get a blood meal and then seek a shaded place along a fence, barn wall or feed bunk or in vegetation to digest it.
Stable flies prefer to feed on cattle. But they'll attack horses, dogs and other animals, too. At times, stable flies can be plentiful along the coast, too, feeding on beach-goers' ankles.
On animals, they feed on the lower portions of the body, primarily the legs and lower belly. On dogs, they feed around the periphery of the ear, leaving the margin scabbed and bleeding.
The stable fly's bite is painful, and cattle try to dislodge them by stamping their feet, switching their tails and twitching their skin. When flies are abundant, they'll try to avoid them by standing in water or bunching up, each trying to get to the center of the group.
Horses likewise kick and stamp to deter these flies. They can make shoeing hazardous for farriers.
Contact your University of Georgia Cooperative Extension county office to learn more about properly maintaining your compost pile and controlling stable flies.
(Nancy Hinkle is a Cooperative Extension entomologist with the University of Georgia College of Agricultural and Environmental Sciences.)