The Tabanidae Family: Horse and Deer Flies
The family Tabanidae encompasses a vast group of insects, with its most well-known members being horse flies and deer flies. These robust, fast-flying insects are a common nuisance, particularly in warm, moist environments where they breed. Females are the ones that bite, using their specialized mouthparts to slice skin and feed on blood, which is essential for developing their eggs. Males, in contrast, are harmless and feed on nectar.
Horse Flies (Tabanus spp.)
Horse flies are typically the larger of the two, with some species reaching over an inch in length. They are stout-bodied and can be black, gray, or brown, often with large, brightly colored eyes that may have horizontal stripes.
- Habitat: Horse fly larvae develop in moist or semi-aquatic environments, such as saturated soil or water, migrating to drier soil to pupate.
- Behavior: These flies are active during the day, especially in sunny weather, and are known for their loud, aggressive buzzing. They often attack the legs and ankles of their hosts.
Deer Flies (Chrysops spp.)
Deer flies are smaller than horse flies, typically under half an inch long. Their bodies are yellowish-brown to black, and they are easily identified by the dark, smoky patterns on their wings and their iridescent green or gold eyes.
- Habitat: Similar to horse flies, deer flies breed in moist environments like wetlands and near streams.
- Behavior: They are particularly known for swarming around the heads and necks of people and animals. Their bite, while often less intense than a horse fly's, is still quite painful.
Other Biting Flies
While Tabanids are the "giant" flies, it's worth noting other species that bite, such as the house-fly-like stable fly (Stomoxys calcitrans), which bites with a sharp proboscis and breeds in decaying vegetation. Black flies (Simuliidae) are another type of biting fly, distinguished by their small, hunchbacked appearance, and are particularly prominent near running water.
How to Identify Giant Biting Flies
Distinguishing between horse flies and deer flies is crucial for understanding their behavior and bite patterns. Here is a table for easy comparison:
| Feature | Horse Fly | Deer Fly |
|---|---|---|
| Size | Larger (up to 1.25 inches) | Smaller (0.25 to 0.5 inches) |
| Wings | Usually clear, or entirely dark in some species | Often have dark, mottled or patterned wings |
| Eyes | Large, often striped or solid-colored | Strikingly iridescent green or gold with dark spots |
| Body | Typically drab gray or black | Yellowish-brown to brownish-black |
| Bite Location | Primarily legs and ankles | Often swarms around the head and neck |
The Risks Associated with Giant Fly Bites
The bite of a giant fly is more than just a nuisance; it poses several health risks, primarily due to the way they feed and the pathogens they can carry.
Painful Bites
Unlike mosquitos that use a fine, needle-like stylet, female tabanids use a pair of razor-sharp, scissor-like mouthparts to slice the skin. This creates a noticeable, often bleeding, wound from which they lap up the blood. The bite is instantly painful, and the wound can be a target for secondary infections if not properly cleaned.
Allergic Reactions
The saliva that biting flies inject contains an anticoagulant to keep the blood flowing. For some individuals, this saliva can trigger an allergic reaction, resulting in localized swelling, intense itching, redness, or even systemic symptoms like headache and nausea.
Disease Transmission
Giant biting flies are known vectors for various diseases, particularly among livestock. While less common in humans, certain species, like the deer fly (Chrysops discalis), can transmit bacterial infections such as tularemia, or "rabbit fever". They can also mechanically transmit blood-borne diseases by moving between hosts during feeding.
Prevention and Management
While eliminating giant biting flies completely is challenging, several measures can help minimize your risk of being bitten.
- Wear Protective Clothing: Long-sleeved shirts, long pants, and a hat can reduce exposed skin. Light-colored clothing is often less attractive to flies.
- Use Repellents: Although less effective than against mosquitoes, some repellents can provide a degree of protection. Apply them to clothing as well as skin.
- Avoid Infested Areas: If possible, stay away from wetlands, marshes, and bodies of water during peak season (typically mid-summer), especially during warmer parts of the day.
- Install Traps: Commercially available traps, often using a dark ball and sticky surface, can be effective in capturing horse and deer flies around properties or livestock areas.
- Eliminate Breeding Sites: If possible, drain or manage areas with standing water, though many breeding sites are natural and difficult to control.
Treating Giant Biting Fly Bites
If you get bitten, follow these steps to manage the symptoms and prevent infection:
- Wash the Area: Clean the bite thoroughly with soap and water to prevent infection.
- Apply Cold Compress: Use a cloth dampened with cold water or an ice pack wrapped in a towel for 10–15 minutes to reduce pain and swelling.
- Use Creams: Apply an antihistamine cream or hydrocortisone cream to the affected area to relieve itching.
- Take Oral Antihistamines: If itching is severe, an over-the-counter oral antihistamine can help.
- Avoid Scratching: Resist the urge to scratch the bite, as this can break the skin and increase the risk of secondary infection.
- Monitor for Infection: Watch for signs of increasing redness, swelling, or pain and seek medical attention if symptoms worsen.
For more detailed information on biting flies and disease transmission, you can consult the Illinois Department of Public Health.
Conclusion: Coexisting with Biting Flies
Understanding what giant biting flies are and how to manage their presence is key to enjoying outdoor activities with minimal risk and annoyance. By knowing the difference between horse flies and deer flies, practicing effective prevention strategies, and treating bites promptly, you can minimize the impact of these persistent pests on your health and well-being. Awareness of their preferred habitats and behaviors empowers you to take control and stay safe.
