Elmer Gray, an extension entomologist and director of the Black Fly Research and Resource Center, spoke with Southern Living about different ways to keep black flies away.
“Black flies are stout-bodied flies, which are closely related to mosquitoes,” Gray said. “Their intense swarming activity around your head and face creates a significant nuisance if you’re trying to enjoy the outdoors.”
Black flies can be identified by their 2 to 4 millimeter shiny black, tan or greenish bodies and humped backs. They can negatively impact wildlife, driving birds such as loons, whooping cranes and snowy owls off their nests and disturb breeding, said Gray.
The insects can also pose a threat to domestic animals, feeding on cattle, horses, sheep, goats, poultry and dogs. Bites from black flies can be toxic to cattle, and poultry can die from blood loss or from being suffocated by flies in the animal’s airway.
According to Gray, the female black fly uses her mouth to snip the skin, often on the head, ears, neck or forehead, though they’ll bite any exposed area. Through the bite, an anti-coagulant is injected, which causes the blood to run.
Bites from black flies can be painful and itchy, lasting from days to weeks. Some people and animals may experience severe reactions or swelling. Contact a doctor immediately if you have an unusual response.
While black flies only live a few weeks and activity drops when temperatures rise into the 80s, the best defense is taking steps to limit your personal exposure, Gray said.
These steps include using repellants on exposed skin and wearing the proper clothing during peak season. Repellants with lemon eucalyptus oil, picaridin and higher concentrations of DEET seem to be most effective, Gray said. However, natural repellants and ultrasonic devices are not effective.
Loose-fitting clothing with light-colored long sleeves, long pants and a hat with fine netting can also provide some protection. For an additional deterrent, wear clothing that has been treated with permethrin.
