When spending time outdoors, the presence of blood-feeding insects can quickly turn an enjoyable moment into a painful experience. Unlike house flies, which are merely nuisance pests, biting flies possess specialized mouthparts designed to pierce skin and draw blood. Female biting flies require a protein-rich blood meal to produce their eggs, driving their persistent pursuit of humans and animals. This article explores actionable strategies, from chemical protection to environmental management, to effectively keep these aggressive insects from biting you.
Understanding the Primary Biting Pests
Several species of flies cause painful encounters, each with distinct behaviors that influence prevention methods. Horse flies and deer flies, belonging to the family Tabanidae, are large, daytime feeders that inflict a noticeably painful bite. They use scissor-like mouthparts to slice the skin, causing blood to pool. These flies are strongly attracted to movement, carbon dioxide, and large, dark objects, frequently buzzing around the head and shoulders.
Stable flies look similar to common house flies but possess a rigid, piercing proboscis. Both male and female stable flies feed on blood, typically targeting the lower legs and ankles of their host. Black flies, often called gnats, are small, dark insects that cut the skin to feed on the resulting blood pool, concentrating their bites around the head and ears. Recognizing the specific pest and its habits is the first step toward successful protection.
Topical Repellents and Application Strategies
The most immediate defense involves the proper use of topical skin and clothing treatments. The Environmental Protection Agency (EPA) registers several active ingredients for safety and effectiveness, including DEET, Picaridin, and Oil of Lemon Eucalyptus (O.L.E.). EPA-registered products undergo testing to ensure they provide reliable protection against various biting pests.
DEET’s concentration determines the duration of protection. A concentration of 30% can provide several hours of defense, which is generally considered the maximum needed for most outdoor activities. DEET should be applied sparingly to exposed skin and clothing, as it can damage synthetic materials like rayon, spandex, and certain plastics.
Picaridin, a synthetic compound, is an alternative that is equally effective against biting flies and mosquitoes. Picaridin is non-greasy, has little odor, and does not damage plastics or synthetic fabrics, making it suitable for application on clothing. A 20% concentration is typically recommended for long-lasting protection against a broad spectrum of insects.
Oil of Lemon Eucalyptus (O.L.E.), or its refined active ingredient p-menthane-3,8-diol (PMD), is a plant-derived option that provides reliable protection comparable to low-concentration DEET for up to six hours. Do not confuse O.L.E. with generic lemon eucalyptus essential oil, which is not EPA-registered and offers shorter protection. Always apply repellents to the palm first before wiping a thin, even layer onto the face, avoiding eyes, mouth, and any cuts or irritated skin.
Physical Barriers and Clothing Protection
Because many biting flies are visually driven and aggressive, covering exposed skin provides a straightforward, non-chemical line of defense. Wearing long-sleeved shirts and long pants made of tightly woven fabrics, such as nylon or densely woven cotton, prevents the insects from reaching the skin. Loose-fitting clothing is more protective than tight garments, as biting insects can often pierce thin fabric stretched directly against the skin.
The color of your clothing is a significant factor, particularly with horse and deer flies, which are attracted to large, dark, moving objects. Opting for light-colored apparel, such as white, tan, or light gray, can make you less visible and less appealing to these pests. Tucking pant legs into socks and cinching sleeves also prevents smaller insects like black flies from crawling underneath clothing to feed.
For maximum protection, clothing can be treated with Permethrin, an insecticide that kills or incapacitates flies upon contact. Permethrin should never be applied directly to the skin but is safe for use on fabric, where it binds to the fibers and remains effective through several washings. A fine mesh head net worn over a wide-brimmed hat provides a crucial barrier against persistent swarmers like black flies and deer flies.
Modifying Local Habitats to Reduce Populations
Long-term management involves reducing the number of flies by eliminating their breeding grounds. Stable flies lay their eggs in moist, decaying organic matter, such as old hay bales, wet grass clippings, and aged manure. Removing or properly managing these materials—for example, by composting them at high temperatures or spreading them thinly to dry out—will break the fly’s life cycle.
Controlling black flies is more challenging, as their larvae require fast-moving, flowing water found in streams and rivers. Since these are large-scale natural habitats, individual homeowners cannot effectively treat the breeding sites; local control often relies on community-wide larvicide programs.
For horse flies and deer flies, which breed near wetlands and ponds, specialized traps can significantly reduce adult populations. These traps typically feature a large, dark object, such as a black ball, that mimics a host and is suspended beneath a collection funnel. When the visually attracted flies land on the dark object, they instinctively fly upward and are captured. Strategically placing these traps in sunny areas between the breeding site and the location you wish to protect offers an effective, chemical-free method to suppress the population.