Deer flies, belonging to the Tabanidae family, are blood-feeding pests. These insects are distinguished by their large, often brightly colored eyes and dark bands across their wings. The painful bite is exclusively delivered by the female fly, which requires a blood meal to produce eggs. Deer flies are notorious for their persistence, making direct deterrence challenging. Practical methods for repelling and avoiding these biting flies focus on personal protection, specialized physical removal, and modification of outdoor habits.
Topical Repellents and Protective Clothing
Standard chemical repellents offer limited defense against the deer fly. Formulations containing DEET, while effective against many other insects, are often mediocre at deterring these biting flies. Deer flies may still land and attempt to bite through the repellent barrier, especially when concentrations are low. Picaridin, a compound, has shown better efficacy against flies than DEET and is a suitable choice for skin application.
For maximum personal protection, a concentration of around 20% Picaridin is recommended, which may provide several hours of protection against various flies. Natural alternatives, such as oil of lemon eucalyptus (OLE), are often touted as repellents, but their effectiveness against the deer fly is highly inconsistent. Relying solely on plant-based oils may lead to disappointing results in areas of high infestation.
The most effective personal defense is clothing designed to eliminate visual attraction and provide a physical barrier. Deer flies are strongly drawn to large, dark, moving objects, as these mimic the bodies of livestock or other prey. Wearing light-colored clothing, particularly white, light tan, or yellow, makes the wearer a less appealing target. Full coverage, including long sleeves, pants, and a hat, is necessary to prevent bites, which often target the head and shoulders.
Designing and Deploying Physical Traps
Given the limitations of topical repellents, specialized physical traps are the most successful strategy for area control. These devices exploit the deer fly’s visual hunting behavior, which involves an attraction to movement, heat, and dark coloration. The most common design is the black ball trap, which mimics a host animal basking in the sun.
The trap typically uses a large, dark, inflatable ball coated with a specialized sticky adhesive, such as Tanglefoot. When placed in a sunny area, the ball absorbs solar energy, radiating heat that further attracts the flies. Flies approach the ball to land and bite, becoming permanently stuck on the tacky surface.
More advanced versions use a black object suspended beneath a cone-shaped canopy. When the fly attempts to bite the dark surface and fails, its instinct is to fly vertically upward toward the light. This behavior guides them into the collection bin, where they are trapped. Traps should be positioned in open, sunny locations near the perimeter of the area you wish to protect, rather than directly in human activity zones, to intercept incoming flies.
Area Management and Activity Modification
Adjusting the timing and location of outdoor activities can reduce encounters with deer flies. These flies are most active during the warmest, sunniest parts of the day, typically peaking between late morning (10 AM) and mid-afternoon (2 PM). Avoiding open, sunny areas during these hours, especially on days with little to no wind, naturally decreases your exposure.
Deer flies breed in moist soil, mud, and near aquatic environments like marshes or ponds. While eliminating large natural breeding grounds is impractical, managing small, stagnant water sources near homes can help. The flies are highly responsive to movement, as it signals a potential host. Limiting rapid or sudden movements when in known fly habitats can reduce the immediate attraction of nearby flies.