Deer flies are aggressive biting pests that can quickly make spending time outdoors miserable. Unlike mosquitoes, which primarily rely on scent, deer flies are visual hunters. They are attracted to a combination of visual cues like movement and color, along with chemical signals like carbon dioxide exhaled by a host. Successfully managing these persistent insects requires a multi-layered approach combining personal avoidance strategies with environmental control and trapping methods.
Understanding Deer Fly Activity and Habits
Deer flies belong to the Tabanidae family. They are typically smaller than horse flies, measuring about one-quarter to one-third of an inch in length. They are distinguished by their brightly colored, often iridescent eyes and the dark, zigzag bands that pattern their wings. Only the female deer fly bites, requiring a blood meal for egg development, while the males feed on nectar and pollen.
The female fly uses specialized, knife-like mouthparts to slice the skin, creating a small, painful wound from which she laps up the pooling blood. This feeding style makes their bites immediately more painful than a mosquito’s bite. These pests are most active during the warmest parts of the day. Their peak season generally runs from late spring through mid-summer, with activity tapering off by late August.
Deer flies thrive in habitats near standing water, which is necessary for their larval development, such as marshes, wooded swamps, and the edges of ponds or lakes. They are strongly attracted to movement, warmth, and the carbon dioxide plume released by warm-blooded animals. This combination of visual and chemical attraction allows them to relentlessly pursue a target, often circling the head and shoulders before landing to bite.
Immediate Personal Protection Strategies
Personal protection starts with minimizing your visual appeal and creating physical barriers. Wear thick, loose-fitting clothing that covers as much skin as possible, including long sleeves and pants. Their mouthparts can easily penetrate thin fabric, but thick materials like denim or canvas offer a greater level of protection.
Clothing color choice is a significant factor in avoidance. Deer flies are intensely attracted to dark colors, particularly blue and black, which they may mistake for a large mammal. Switching to light-colored or white clothing can substantially reduce the number of flies that target you. Wearing a light-colored hat is also effective, as the flies often target the highest point of a moving object, frequently the head or neck area.
When considering chemical defense, many standard mosquito repellents containing low concentrations of DEET offer limited success against deer flies. This is because the fly’s visual hunting method often overpowers any olfactory repulsion from the chemical. However, repellents containing 20% Picaridin may be more effective against biting flies than DEET and can offer up to eight hours of protection.
Picaridin, a synthetic compound derived from the pepper plant, is considered a better option for biting flies. Oil of Lemon Eucalyptus (OLE) is often recommended for mosquitoes, but its effectiveness against deer flies is not consistently demonstrated and is a less reliable defense. The most immediate personal strategy, especially when flies are swarming, is to reduce movement, as a stationary target is significantly less appealing to these visual predators.
Area-Specific Control and Trapping
Reducing the local population of deer flies is best achieved through targeted trapping, as eliminating their breeding grounds in wet areas is often impractical. The most successful methods capitalize on the flies’ attraction to dark, warm, and moving objects. Traps designed for deer flies, often called canopy or T-traps, use a dark-colored sphere or object suspended from a post.
A common and effective homemade device involves a dark blue or black object, such as a rubber ball or an inverted flowerpot, coated with a sticky insect trapping adhesive. This object is suspended three to six feet above the ground in a sunny, open area where the flies are active. The dark object absorbs solar heat and is mistaken by the flies for a host animal.
When the flies attempt to land on the sticky surface, they become trapped. If they miss, their natural escape instinct is to fly upward into a collection device positioned above the dark lure. Traps can be highly efficient, with commercial models sometimes covering areas up to two and a half acres. For personal protection, a sticky blue cap worn on the head can work as a highly localized trap, drawing flies away from the wearer’s skin.
While environmental control of breeding sites is impractical, minor mitigation can still be helpful around a yard or recreational area. Keeping grass and vegetation trimmed short eliminates resting spots for the adult flies during the night. The strategic placement of traps in sunny, high-traffic areas remains the most reliable method for reducing the immediate deer fly population.