What Attracts Horse Flies: Top Lures & Prevention Tips

Horse flies are notorious for their painful bites, and they can be a serious nuisance to humans, livestock, and other animals. Understanding what attracts these pesky insects can help you avoid unwanted encounters and minimize their impact on your outdoor activities.

One key factor that draws horse flies to their targets is the detection of carbon dioxide (CO2) that animals and humans exhale. Besides CO2, horse flies are attracted to warmth, motion, and dark colors. By identifying these factors, you can take measures to reduce your chances of being bitten.

In general, horse flies are most active during daylight hours and prefer warm, sunny conditions. They are often found near bodies of water, such as ponds or marshes, as their larvae rely on moist environments to develop. So, being aware of your surroundings and the factors that attract horse flies can help you stay bite-free while enjoying the outdoors.

Understanding Horse Flies

Horse flies are a type of biting fly belonging to the Tabanidae family. They are known for their annoying and painful bites, which can be an issue for humans, livestock, and wildlife. To better understand their behavior and find ways to avoid them, let’s look at some of their features:

• Size: Horse flies are generally medium to large-sized flies, making them easy to spot. They can range from 0.6 to 1 inch in length.
• Color: Most horse flies are drab browns, grays, and blacks, allowing them to blend in with their surroundings.
• Eyes: Their large compound eyes are one of their most distinctive features, covering most of the head and providing a wide field of vision.
• Wings: Horse flies have one pair of wings, which enable them to fly swiftly and silently.

Horse flies are attracted to a variety of factors, such as movement, warmth, and color. The female horse flies rely on a blood meal for their reproduction, which is why they bite. In comparison, male horse flies feed on nectar and do not bite. To help keep them away, it’s essential to be mindful of the following:

• Movement: Since they detect moving objects, minimizing activity can help keep them at bay.
• Color: Horse flies are drawn to dark colors, so wearing light-colored clothing may make you less attractive to them.

Understanding these features and habits of horse flies can help you be better prepared when encountering them. By taking the right precautions, you can minimize the chances of being bitten and maintain a more comfortable outdoor experience.

The Biology of Horse Flies

Life Cycle

Horse flies have a four-stage life cycle consisting of egg, larva, pupa, and adult. They start by laying their eggs in damp soil or vegetation near water sources like creeks and streams. The larval stage, which lasts up to a year, involves the horse fly living in the soil, feeding on organic matter and small organisms. At the end of this stage, it turns into a pupa, which typically lasts for a few days or weeks before the horse fly emerges as an adult.

Diet and Hunting Behavior

Adult horse flies feed on nectar and plant juices. However, female horse flies require a blood meal for successful egg production. They use their sharp mouthparts to bite and feed on the blood of animals, especially livestock and humans. Their bite can be painful and irritating. On the other hand, male horse flies don’t bite and prefer to rely on nectar and plant juices for sustenance.

Reproduction

After acquiring enough blood meals, female horse flies are ready to reproduce. They lay their eggs in moist soil or vegetation near water sources, where larvae can thrive and find food. The number of eggs laid can vary, with some females laying over a thousand eggs in a single breeding season.

Differentiating Between Male and Female Horse Flies

• Male horse flies:

  • Do not bite
  • Have larger, widely separated eyes

• Female horse flies:

  • Bite in order to obtain blood meals
  • Have smaller eyes that are closer together

Habitat

Horse flies prefer habitats with water, moisture, and vegetation, such as creeks, streams, pastures, and damp areas. Their larvae thrive in soil and require moisture for survival, while adult horse flies need access to plant juices and sources of blood meals for sustenance.

Why are Horse Flies a Problem

Bites and Associated Problems

Horse flies are more than just a nuisance; their bites can cause some serious problems for both humans and animals. When a horse fly bites you, it can be quite painful due to their slicing mouthparts. In addition to the pain, horse fly bites can lead to:

• Skin reactions: Swelling, redness, and an itchy rash may develop around the bite.
• Infections: If not properly cleaned, horse fly bites may become infected.

Here are a few examples of how horse fly bites affect different people:

• Sensitive individuals: For those with allergies or sensitivities, horse fly bites can cause more severe reactions.
• Children: Due to their smaller size and developing immune systems, children may experience more intense reactions to horse fly bites.

Effect on Livestock and Pets

Horse flies don’t only bother humans, they also pose a significant problem for livestock and pets. For example:

• Livestock: Horse fly bites lead to stress, discomfort, and reduced productivity in animals such as cows, horses, and sheep.
• Pets: Dogs and other outdoor pets may also be affected by horse fly bites, adding discomfort and potential health risks.

Some measures to help control these pests and protect your animals include:

• Using fly repellent products, like citronella spray
• Adding fly sheets and masks to horses
• Turning animals out at night, when horse flies are less active
• Providing shelter or canopy trees for shade and protection

By taking measures to control horse flies, you can minimize the impact these pests have on your animals and yourself, ensuring a more comfortable and healthy environment.

Preventing Horse Fly Bites

Protecting Livestock and Pets

To protect your livestock and pets from horse fly bites, turn them out at night instead of the day, as horse flies are daytime biters. Additionally, provide shelters or canopy trees far from wooded edges of pastures or marshy areas to help minimize bite incidents.

For horses specifically, consider using physical exclusion methods such as fly sheets, masks, and boots to keep fly pests from accessing their face, legs, or body. Installing fans in the stable area can also interrupt the flight and prevent some flies from landing.

Protecting Humans

To protect yourself from horse fly bites, here are some recommendations:

• Wear protective clothing that covers your skin, such as long sleeves, pants, and hats.
• Apply insect repellent containing DEET, picaridin, or oil of lemon eucalyptus to exposed skin.
• Avoid wearing dark clothing or flowery patterns, as these may attract horse flies.

To help control horse fly populations, consider implementing the following strategies:

• Keep your area clean and free of standing water to prevent breeding grounds.
• Use traps specifically designed for horse flies, such as those using visual or chemical attractants.
• Maintain proper yard maintenance by keeping grass trimmed and clearing away brush and debris.

Remember, prevention is key in protecting both your livestock, pets, and yourself from horse fly bites. With these tips in mind, you can minimize the chances of getting bitten and ensure a more enjoyable outdoor experience for all.

Controlling and Getting Rid of Horse Flies

DIY Home Remedies

You can try some simple home remedies to control and get rid of horse flies. One option is using vinegar as a trap. Fill a container with equal parts water and vinegar, and add a few drops of dish soap. Place this trap near the area where you’ve noticed horse flies.

Another effective method involves using essential oils like peppermint, citronella, and eucalyptus. Create a fly repellent spray by mixing a few drops of these oils with water in a spray bottle. Apply this to your horse, stable, or yourself to deter flies.

Commercial Insecticides and Repellents

There are various insecticides and repellents available on the market for controlling horse flies. Some common options include:

• Citronella oil based products, which can be found in sprays, leg bands, or leggings for your horse
• Eucalyptus oil based products, such as sprays, that you can apply on your horse or stable
• Fly sheets, masks, and boots for physically preventing flies from accessing your horse

Make sure to follow the product instructions for proper use and application.

Professional Pest Control

If you’re unable to effectively control horse flies with DIY remedies or commercial products, it may be time to consider professional pest control. Professionals can assess your property and provide tailored solutions to effectively control and eliminate horse flies. Hiring a professional may especially be necessary if your horse fly problem is severe or persistent.

Remember to always choose a reputable pest control company and inquire about their methods for dealing with horse flies, as well as any safety measures they take to protect your animals.

Identifying Other Types of Flies

Deer Flies

Deer flies are small and agile, making them difficult to swat away. They can be identified by their distinct features:

• Yellow or brown colored bodies
• Dark bands on wings
• A preference for warm, sunny areas

House Flies

House flies are a common nuisance in homes and stables. To identify them, look for these characteristics:

• Dark gray body color
• Red eyes
• V-shaped patterns on their abdomen

Comparison Table: Deer Flies vs House Flies

To deal with these nuisance flies, it’s important to identify them correctly and use appropriate control methods. A combination of good farm management, proper waste disposal, and targeted treatments can help reduce their impact on your horses and stable environment.

Reader Emails

Over the years, our website, whatsthatbug.com has received hundreds of letters and some interesting images asking us about these insects. Scroll down to have a look at some of them.

Letter 1 – Western Horse Fly

Large Fly
Location:  Death Valley, California
August 27, 2010 4:33 am
We encountered some large – about 20cm long – flies in death valley, california whilst on holiday there. We were walking along a trail next to a dry creek. The flies were black and light grey and one landed on my back and penetrated my shirt so that I felt a pinch. Just curious as to what they are.
Andy

Hi Andy,
You may compare your image of a Western Horse Fly, Tabanus punctifer, to images posted to BugGuide, but there is no information on the specifics of the species.  You may, however, read about Horse Flies in general on the genus page of BugGuide.  Only the female Horse Flies bite and suck blood from warm blooded animals.  Charles Hogue, in his excellent book Insects of the Los Angeles Basis, writes extensively about the Western Horse Fly.  He observes:  “The adults are large robust flies nearly 3/4 inch (20mm) in body length.  The male possesses very large eyes, which meet on the midline of the head, making it appear to be nearly all eye;  the back of the thorax is black except for a fringe of white hairs along the side and rear borders.  The female differs in that the eyes are separated and the back of the thorax is all white or pale cream.”  Your photo is that of a female, hence the bite through your shirt.  The larvae of the Western Horse Fly develop in water, so even though your email indicates this sighting was in Death Valley, we suspect it may have been close to either Salt Creek or Devil’s Hole.  Hogue has additional information:  “Because they possess a voraious appetite for the blood of horses and cattle, the female flies may be extremely bothersome, especially when numerous.  They have been observed biting rhinoceroses, tapirs, and hippopotamuses at the Los Angeles Zoo.  They occasionally bite humans, with painful results.  Natural saccharine fluids, such as fruit juices and nectar from flowers nourish the nonbiting males and also serve as a diet supplement for the females.”

Letter 2 – What plants attract a male Horse Fly???: Umbel and Composite Flowers

Subject (please be succinct, descriptive and specific):  children’s book with male horsefly character
Date: 02/22/2020
Time: 04:08 PM EDT
Your letter to the bugman:  Hi – I’m writing a children’s book and one of the main characters is a male horsefly. I’ve been trying to find what types of plants male horseflies (specifically in the area of Kentucky) would be most attracted to.  I haven’t been able to find anything so far.  Any help would be appreciated.  Thank you.  Diana Wilburn

Dear Diana,
Most of the images we have of male Horse Flies were not taken on plants, however, we did locate an image in our archives of a male Black Horse fly from nearby Indiana that was taken on the leaf of a corn plant.  According to BugGuide:  “adult females feed on vertebrate blood, usually of warm-blooded animals; males (also females in a few spp. in all 3 subfamilies) visit flowers.”  Of the Black Horse Fly, Tabanus atratus, BugGuide notes:  “males, which lack mandibles, feed on nectar and plant juices.”  We suspect umble-shaped flowers in the family Apiaceae including parsley, carrots, dill and Queen Anne’s lace that attract many pollinating flies would also be a choice for Horse Flies, and we have images in our archive showing a Male Horse Fly (Hybomitra cincta) on a parsley blossom.  Other images we located online of male Horse Flies feeding on other umble blossoms include Nature Picture Library where it is on fennel, iStock Getty Images where the male Horse Fly is feeding on Hogweed, and Wikipedia where it states:  “they mainly feed on nectar of flowers (especially of Apiaceae species).”  Composite flowers in the family Asteraceae, are also good food sources including this Adobe Stock Images example of a male Horse Fly on Goldenrod or this Alamy image of a male Horse Fly on a coneflower.

Letter 3 – Western Horse Fly

Western Black Horse Fly
Good afternoon!
I was perplexed as to what type of fly this was until I found it on your site, a female western black horse fly! It was about 1.5 inches long and apparently very noisy (my husband heard this critter buzzing around him and then spotted her on our fence in our backyard in Sacramento, CA.). I’ve never seen a fly that had fur like this!
TC

Hi TC,
We are always thrilled when new visitors to our site actually take the time to try to research the object of their desire to identify rather than to just email us directly. Congratulations on the successful identification of a female Western Horse Fly, Tabanus punctifer.

Letter 4 – Western Horse Fly

Western Black Horse Fly
Hi Everyone!
Love the site as most everyone does. I look up insects
frequently for identification, research, and fun. Thanks
so much. I found this fly in our backyard of sunny Santa Barbara,
CA, and by looking up your site I think I pegged him to be
a Western Black Horse Fly, Tabanus punctifer . Confirmation
would be great. Enjoy the pics and thanks again for your hard
work!
Christopher

Hi Christopher,
Thank you so much for submitting your image of a female, not
male, Western Horse Fly. There is a space between the eyes
of the female, and the eyes of the male are closer set. Compare
your image to this male Western Horse Fly on BugGuide.
The male also has a darker patch on the thorax.

Letter 5 – Western Horse Fly

Huge Black Fly for ID …
Location: Applewood, Golden, Colorado
July 24, 2011 7:36 pm
Hi,
Great site you have here! My daughter and I caught this huge black fly in our back yard today, and she would like to know what kind it is.
It is very large (as far as houseflies go), and has a tan / grey area on its back, and also leg joints of the same color.
I tried to get a good picture of its eyes as well, as thet are quite stunning, with horizontal stripes accross them. I could not get an image that did them justice.
Thank you for your time,
Charley and Hannah
Golden, Colorado
Signature: Charley and Hannah

Dear Charley and Hannah,
You have captured a female Western Horse Fly, Tabanus punctifer.  The female can be differentiated from the male by the spacing between the eyes.  There is space between the eyes of the female but the males eyes meet in the middle.  Female Western Horse Flies are blood suckers that feed on warm blooded animals.  If livestock and game are not available, they will bite humans.

Daniel,
Thank you so much for the speedy reply. It really made Hannah’s day!
Here is the drawing that she made to save for her bug journal.
We catch, study and release a lot of Swallow Tail Butterflies in our back yard too (see second pic). Is there a similar trick to determining the sex of that species?
Thanks again,
Charley