Are Horse Flies Dangerous? Uncovering the Truth

Horse flies and deer flies are known for their bothersome presence around humans, livestock, and wildlife.

These insects are bloodsuckers, often causing painful bites in their quest to feed.

While their annoying nature is undeniable, the question arises: are horse flies dangerous?

The concern over their potential to transmit diseases is valid, as their bloodsucking habits may introduce pathogens to their hosts.

Despite this risk, it’s important to understand the biology of these insects to properly assess their impact on public health and learn how to minimize the chances of being bitten.

Differentiating between horse flies and deer flies can help in understanding their potential hazards.

Horse flies are typically larger, with clear wings and grayish-brown thoraxes, while deer flies are smaller, sporting tinted wings and greenish-yellow thoraxes with dark stripes.

Their varying appearances can clue individuals into which type of fly they may be dealing with and what precautions to take.

Basic Information about Horse Flies

Physical Characteristics of Horse Flies

Horse flies belong to the Tabanidae family and are known for their large size and distinct appearance. Some common features of horseflies include:

• Size range: 3/4 to 1-1/4 inches long
• Large, brightly colored eyes
• Clear or solidly colored wings
• Grayish-brown or blackish body color

Gender Differences: Male Vs. Female Horse Flies

There are notable differences between male and female horse flies. Key distinctions can be found in the table below:  

Male horse flies have large eyes, which almost touch, while female horse flies have smaller and more separated eyes. The primary difference lies in their feeding habits.

Horse Fly Bites

Why Horse Flies Bite

Horse flies bite humans and animals for one primary reason: to obtain blood. Female horse flies need the nutrients in their blood to produce eggs. These flies have specialized mouthparts to effectively access blood from their victims.

They use a scissor-like mandible to cut through the skin, which can cause significant pain for the one being bitten.

Symptoms of Horse Fly Bites

Horse fly bites can lead to various symptoms:

• Pain: The bite is usually painful due to their cutting mouthparts.
• Redness: The bitten area often becomes red and inflamed.
• Swelling: Bites can lead to puffiness and swelling around the bite site.
• Itching: As with many insect bites, itching is a common symptom.
• Rash or hives: Some individuals may develop a rash or hives near the bite.

In some cases, horsefly bites can lead to more severe symptoms, including:

• Fever: A high temperature may indicate an infection or an allergic reaction.
• Vomiting: Severe reactions to horsefly bites may cause vomiting.
• Bacterial infection: Bacteria from the fly’s mouthparts can enter the bite wound, leading to infection.

While horse flies don’t directly transmit diseases, the risk of bacterial infection and potential allergic reactions makes their bites concerning.

In horses, horse fly bites have been associated with transmitting equine infectious anemia.

Prevention and Control

Protecting Livestock and Pets

In summer, horse flies can be quite bothersome to livestock and pets. To protect them from these pests, consider the following:

• Use fly sheets, masks, and boots to physically exclude flies from contacting your animals.
• Place fans in stable areas to interrupt flight and make it difficult for flies to land.
• Provide your animals with deep shade or housing, which also helps manage water sources and reduce exposure to aquatic biting flies¹.

Effective Traps and Repellents

Various methods can help control horse populations, including some traps and repellents. For example:

• Horse Pal and Epps Biting Fly Trap can be effective in reducing horse fly populations.
• Insect repellents containing DEET or picaridin can offer some protection against deer flies.
• Using light-colored clothing may help reduce the attraction to and bites from these flies.

Here’s a comparison table of these repellent and trap options:

By using these preventative measures and techniques, you can help reduce the risk of your animals and yourself being affected by horse flies.

Horse Fly Life Cycle

The Breeding Environment

Horse flies are known for their blood-sucking behavior during daylight hours. They belong to the family Tabanidae and thrive in moist environments, such as marshes, swamps, and damp areas.

Some characteristics of their breeding environment include:

• Wet areas with standing water
• Presence of plants and decaying organic matter
• Close proximity to animals, as they provide a source of protein for the female horse flies

Development from Eggs to Adult Horse Flies

Horse flies undergo a complete life cycle, including the stages of eggs, larvae, pupae, and adults. Here is an outline of their development:

1. Eggs: Female horse flies lay their eggs on plants near water bodies or in marshy areas, providing the larvae with a suitable environment to develop.
2. Larvae: Once hatched, the larvae consume organic matter, including decaying plants and small organisms like mosquito larvae and ticks. In some cases, they also feed on frogs.
3. Pupae: After reaching a certain size, the larvae form pupae and undergo metamorphosis. At this stage, they are relatively inactive and can remain in the pupal case for several days to months.
4. Adult Horse Flies: They emerge from the pupae and feed on flower nectar and plant sap for energy. Females require blood meals for reproduction, and their bites can be painful for animals and humans alike.

Potential Health Risks

Allergic Reactions

Horse flies are known to bite both humans and animals, such as pets and equine. While their bites can be painful and cause itching, some individuals may experience more severe reactions. Allergic reactions to horsefly bites can include:

• Wheezing: Difficulty breathing, potentially requiring medical attention.
• Dizziness: Feeling light-headed or unsteady on your feet.
• Swelling: At the site of the bite or, in severe cases, in the face or throat, which could lead to difficulty swallowing.

Infections and Complications

The risk of infection from horse fly bites is relatively low compared to other insect bites such as mosquitoes or house flies. However, if proper care is not taken, complications can arise.

Bacteria can enter the bite wound and lead to infection. To minimize these risks, follow these simple steps:

• Clean the area: Use soap and water to disinfect the bite.
• Ice pack: Apply an ice pack to reduce swelling and numb pain.
• Avoid itching: Scratching the bite can introduce bacteria and increase the risk of infection.

In some cases, horsefly bites may transmit diseases such as swamp fever in North America. This disease mainly affects equine populations and is rare in humans.

To protect yourself from horse flies when outdoors, especially in hot and swampy environments, consider using insect repellents containing DEET.

It’s essential to remain vigilant and take necessary precautions when spending time outdoors, particularly in areas with a known presence of horse flies.

Conclusion

In conclusion, horseflies are considered nuisances due to their painful bites and intimidating appearance. These insects raise valid concerns about their potential dangers.

They don’t directly transmit diseases like mosquitoes, but since the females consume blood, they pose various health risks. The bites are painful and can cause discomfort, itching, and localized swelling.

These bites can also trigger an allergic reaction and can lead to more severe symptoms, such as wheezing, dizziness, and extensive swelling.

The bites also add the risk of infection because the bacteria from the flies’ mouthparts can enter the wound.

Use the tips and tricks mentioned in the article to avoid these bites and to be safe from these insects.