Great Gray Owl Pest Control

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Identification of Horse Flies

Flying insects have tormented humans and animals for thousands of years, especially blood-feeders such as the female horse fly (Chrysops relictus). These winged villains of the invertebrate order Diptera (true flies) are relentless in their vicious pursuit; silently stalking, then fiercely striking and inflicting painful wounds with their razor-sharp teeth. Knowing how to identify horse flies and protecting yourself while in their habitat lessens your chances of becoming a meal for these flying terrors. 

Know Your Predator


Requiring blood to produce her eggs, the female horse fly is the culprit who bites and feeds on blood while her harmless mate is gathering nectar, oblivious to her rampage. Easily recognized when you know what you’re looking for, female horse flies have thick, dark brown to black bodies that measure up to an inch long, with broad heads featuring bulging, brilliant iridescent green eyes. Their wings are either dark or completely clear. Rather than suck blood through a tube like mosquitoes, horse flies slice through skin with their powerful mandibles, and lap up the blood.


Proceed With Caution


Ponds, marshes and streams are horse fly breeding grounds. Female adults are found in salt marshes, swamps, bogs, shoreline, woodlands and forests. They feed during the day and prefer hot, sunny, wind-free days. Although their strong wings can take them several miles, horse flies typically remain within a two-mile radius. They attack dark, moving objects and congregate on paths and roads to take breaks from the carnage. On windy or cooler days you’re less likely to have a showdown with a horse fly.


Outsmarting the Enemy


When you’re camping, hiking or just strolling through horse fly habitat, preparation is key. Protective clothing and fly masks constructed of no-see-um midge netting are a prerequisite. Also, wear lighter-colored clothing. Many different insect repellents may work, but look for those that specifically state on the label they protect against horse flies. The nontoxic deer fly trap patch worn on the back of a hat is another clever option; it attracts them, then captures them on a sticky pad. Fly masks are available for horses.


Don't Mess With My Relatives


Evil cousins, the horse fly and deer fly, are two of the 4,500 members of the family Tabanidae. A tad smaller than the horse fly, the deer fly has yellow and black on its body. Primarily distinguished from the horse fly by its patterned wings, the deer fly has the same predatory modus operandi, seeking out humans, as well as deer and other mammals to feast upon.


Once Bitten, Twice Shy


Deet-based repellents don’t always stop horse flies when they’re in attack mode. After experiencing what is known as the “ice pick bite” from a horse fly, most people will do anything to avoid a second encounter. The bite site is red, raised and intensely itchy and painful. The pain usually subsides after a couple of days, but seek medical attention if signs of infection are present, such as inflammation, increasing pain and the forming of pus. Some people are allergic to the anticoagulant the female injects at the bite site and develop severe lesions, high fever and even disability.

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