horse with a fly mask
Stable & Pasture

5 ways to get rid of horseflies

What is a horsefly, you ask? It’s a biblical curse on wings, is what it is.

But biologically speaking, it’s a stoutly built fly, the female of which is a bloodsucker and inflicts painful bites on horses and other mammals, including humans.

Adult horseflies typically eat nectar, but the females require a blood meal before they’re able to reproduce effectively.

Horsefly bites are really painful because their mouthparts are used for tearing and lapping, as opposed to piercing the skin and sucking the blood out of a pinhole, as mosquitoes do.

The horseflies use their scissor-like pincers to slash their way into your skin, their saliva acting as an anticoagulant preventing your blood from clotting – and it’ll even keep the blood flowing after the fly has left.

Wikipedia describes their mouthparts as “a stout stabbing organ with two pairs of sharp cutting blades, and a sponge-like part used to lap up the blood that flows from the wound”.


Female horseflies are very persistent.

They will continue biting a host until you kill them or they get their fill of blood. An exceedingly cruel and annoying attitude, if you ask me.

They’ll also need about six days to digest their meal and, yeah you guessed it, then they’ll be back for seconds.

The thing I hate most about them is that they’ll even chase you around once they’ve decided you’re the source of their next meal. Even when you go swimming and dive under the water, those little f***ers will wait for you to come up for air.

They’re notable strong fliers and are much faster than blackflies or mosquitoes – this also makes them even more annoying.

Horseflies are the bane of runners, cyclists and riders in summer.

You can try to outrun them, but know this:

  1. They’re attracted to movement and hunt by sight (not by scent like mosquitoes).
  2. They’re attracted to dark colours, especially blue apparently.
  3. They’re territorial, so even when you outrun one, you’ll enter the territory of the next one.
  4. They’re attracted to carbon dioxide – probably why they love people who exercise outdoors.

They don’t just follow you; these mofos have a tendency to ping off your head – a behaviour that is outright maddening!

They’ll also burrow into your hair to find skin.

Believe me, these buzzers deserve to be called every curse word you can think of!

What does a horsefly look like?

As one of the biggest flies in the world (!!!), they’re relatively easy to identify (not in the least by their pissy attitude about chasing you around).

Their colour varies from dark brown to grey to black.

They have large eyes (that look very alien-like) that can be green or black. The males have those huge wraparound eyes and the females’ are separated.

Horseflies belong to the same family as deerflies, which can be distinguished from horseflies by their more colourful bodies.

When is it horsefly season?

Whenever the weather turns hot and humid you can expect the horseflies to be out in force. In some parts of the world, this is all year!

In colder regions, the horseflies will take a break from reproducing in winter, but in tropical regions, they’ll keep reproducing all year.

Horseflies are found all around the world, with the exception of the polar regions and a few islands, like Iceland, Hawaii and Greenland.

Horseflies mostly occur in warm weather with moist locations for breeding, though they are also found in everything from alpine meadows to deserts.

The females will lay the eggs on stones or vegetation near water.

The clusters can contain up to 1000 eggs that are white at first and darken with age.

It takes the larvae about six days to hatch, after which they fall into the water or moist ground.

Horseflies will typically mate in swarms (called mating swarms), the occurrence of which is highly dependant on the specific species.

What does it feel like to be bitten by a horsefly?

In one word: nasty.

I’m no stranger to being bitten by horseflies and, I once got bitten on the leg and, I could have sworn I’d been shot in the leg.

The large mammals horseflies prefer (horses, cows etc.) are usually powerless to dislodge the flies once they’ve bitten, so they haven’t really had a need to develop a more discreet bite.

And usually, where there’s one horsefly, there are more. So, RUN!

In even worse news, horsefly bites can get infected quite easily. Because they slash their way into your skin and leave a shredded mess behind, it’s easy for bacteria to get in.

Recovering from a horsefly bite typically takes a lot longer than recover from other insect bites.

You can also be allergic to horsefly bites. Oh, the joy.

An infected bite will swell up, be red and painful, and will most likely ooze. Go see your GP.

If you feel squeamish, dizzy, weak, wheezy or have difficulty breathing, nauseous, notice a blotchy skin rash or severe swelling that can even be visible on your lips and tongue, get medical help immediately!

Animals distraught by horsefly bites will try to hide in shrubs and thickets or even go into the water in an attempt to get away from them.

Are horsefly bites dangerous?

Horseflies are known to spread blood-borne bacterial, viral, protozoan and worm diseases of mammals.

However, for humans, being bitten by a horsefly is most often just painful as heck.

Obviously, if it gets infected or you’re allergic, as described above, then yes it can be dangerous.

Horsefly bites can be dangerous to equines because they carry equine infectious anaemia, also called swamp fever.

This is a life-threatening disease for horses.

Your horse may experience fever, haemorrhaging (bleeding) and general illness. Then again, your horse may experience no symptoms but still be able to transmit the disease to other horses, mules and donkeys.

Horseflies are also known to transmit anthrax among cattle and sheep, and rabbit fever (tularemia) between rabbits and humans.

Blood loss is a common problem when there are a lot of horseflies around and it can even decrease the production of milk in dairy cattle.

How to relieve a horsefly bite.

Use an antiseptic spray to rinse out the bite – since you know how to maintain a first aid kit that serves both horses and humans, this will be easily available to you!

Rinse generously to get out any bacteria because that’s what makes cuts sting and burn.

You may want to rinse it several times a day until the wound begins to naturally close and bacteria will have a harder time getting in.

Rinsing it often even after it’s closed can help it heal faster and decrease the chances of it getting infected.

You can take a normal painkiller if it hurts a lot and take anti-histamines to help with the itching if you need to.

If it swells up and feels hot, you can use a cold cloth or an ice pack to try and help.

The bite can leave a bruise. Keep an eye on it for signs of infection; redness and swelling that doesn’t go down, the skin feeling hot, excessive pus, a foul odour.

At the first sign of any unusual symptoms – as I described above – go to the doctor. Better safe than sorry.

What to do when your horse gets bitten by a horsefly?

When your poor horse is subjected to horsefly bites, the first thing to do is to rinse out the bites with an antiseptic. You may also want to put on some antiseptic ointment to help it heal.

Just like if you get bit by one yourself, keeping it clean and preventing bacteria from getting into the bite is important.

Keep an eye on the amount of swelling and how hot the area around the bite is.

Knowing and logging your horse’s base vitals is the standard practice of any smart horse owner. When you know what’s normal, you’ll be able to tell when something is off.

If your horse has been bitten, especially when there are many bites, give him some time off from riding or hard work.

Many fly bites can make him feel tired and lethargic from the blood loss, not to mention sore from all the bites.

How to get rid of horseflies.

You can control an infestation of horseflies by using traps and fly predators.

A Manitoba fly trap, also known as a canopy-style fly trap, is typically used when you have pastures with large animals like horses and cattle.

The trap was invented by an entomologist (bug scientist) in the 1970s, and it uses fly behaviour to trap the flies rather than insecticides or chemical bait.

You can buy ready-to-use traps or build your own Manitoba fly trap quite easily with a hula-hoop, some mosquito netting and a rubber ball.

I’m lazy, so I prefer to buy my traps already made and save time and effort.

But if you want to save money or take on a fun project, you can easily spend an afternoon building a few fly traps.

The Manitoba fly trap works best with a black ball (or another black object) hanging suspended under the netting. It’s important that it’s black so that it absorbs heat, which attracts the horse- and deerflies.

The flies will land on it, thinking it’s the underbelly of a horse or a cow, and when they realise it’s not a possible food source, they’ll take off and fly straight up and into the trap where they’ll eventually die of dehydration.

When the trap gets full, simply empty it out and put it back in the field.

A Malaise trap is a tent-like structure that works on the same principle as the Manitoba fly trap, but it’s usually a bit bigger.

Then there’s also the ball fly trap. The black ball is covered in sticky glue that catches the flies when they land on it. Rise and repeat.

Where should you place your horsefly trap?

Most important is to make sure your horses can’t get to the fly trap because they’ll have that thing down in a matter of moments when they try to play with the ball or use it as a scratching post.

You can place your traps around the arenas and stables where people and horses mostly spend time.

The bigger the area you want to protect from flies is, the more traps you’ll need.

Check with the manufacturer how big of an area their traps cover. If you’re building your own trap, compare it with ready-made traps to see how many you need.

If you’re in peak fly seasons, you’ll need to go out and check/clean your traps often – sometimes several times a day. In really hot and humid areas your traps may fill up several times a day.

If you have chickens, you can feed the dead flies to them or simply leave them out for other insects and animals.

X fly traps to use around your stable and paddocks.

Reusable ranch fly traps.

You can buy these in larger packs on Amazon.

My favourite traps are the reusable ones. Yes, they’re kind of disgusting to empty out, but they create no waste (other than the dead flies), so I don’t have to worry about adding to the plastic waste or anything like that.

They’re easy to handle, don’t weigh much, are pretty durable and they fold up easily for storage during colder months. Since you put your own bait into the fly trap (you can use food scraps), it’s non-toxic and safe around animals. You can also move the traps around easily, putting them in the areas that have the most flies.

Disposable fly traps.

You can find these on Amazon.

These work with much the same principle as the ranch traps, but instead of emptying the trap when it’s full, you just chuck the whole thing in the bin. This also comes with the bait already in the bag, and all you have to do is add water. The included fly bait is non-toxic and attracts a variety of flies, but undetectable to humans.

To use it, you open the screw-top, add some water and hang it where you’ve got a fly problem. The bags attract flies from as far as 30-40 feet away and can hold up to about 30,000 flies. When the trap is full, screw the lid back on and throw it in the bin.

What are fly predators?

Well, first of all, horseflies are not without natural predators.

Birds eat both the adults and the larvae, nematodes and wasps parasitize the larvae, and spiders and wasps also catch solitary adults (the wasps take them back to feed the nest).

Fly predators are nature’s own enemy of all common manure and rotting organic matter breeding pest flies (so, they work on more than just horseflies).

Fly predators serve as a major check of pest fly populations by destroying the next generation of flies in their immature pupa (cocoon) stage.

The fly predators are tiny, biteless and stingless, and don’t become pests themselves.

Because of their small size, and the fact that they live near manure where the pest fly pupa are, they go virtually unnoticed.

You can buy fly predators to help control your pest fly populations. Keep in mind that they don’t work on current infestations as they attack the pupa, not the adult flies.

So, when you’re buying them remember to think ahead and get them for prevention and maintaining low pest fly populations.

If you’re currently swamped by pest flies, use traps to reduce the adult populations and offer your horse immediate relief.

Keeping chickens is also an effective and natural way to keep bug populations low at your stable.

How to stop horseflies biting you and your horse.

Wearing loose clothing can help deter horseflies from biting you, though if the flies are persistent they will find the parts of you that aren’t covered, such as your hands, neck and scalp.

Since they prefer to fly in sunlight (as they hunt by sight), dark and shady areas can also help provide some safe haven.

Generally, you and your horse will be left alone at night when the horseflies are inactive.

To protect your horse, a bug rug is really the best thing. And there’s research showing that the zebra print rug is the most effective in deterring biting flies.

When you’ve got a lot of horseflies:

  • Put a fly mask on your horse.
  • Keep your horse blanketed to reduce the surface area vulnerable to the flies – the zebra pattern has proven effective in research for preventing biting flies.
  • Keep your horse indoors during the worst time of day and consider letting your horse out once the horseflies become less active at night.

One more thing you can do is to use nature’s own bug protection.

Sprays aren’t super effective against horseflies since they hunt by sight and carbon dioxide, and they don’t seem to be as vulnerable to scent as mosquitoes.

And some horses can just be such expert bug rug destroyer’s that it’s challenging and expensive to keep them rugged (even if it is for their own good!).

If you’ve got a mudhole in the paddock – maybe add a bit more water to it to make it even muddier – let your horse roll in the mud as often as he wants.

When he’s covered in mud it’ll dry to form a protective shield around his skin and discourage bugs from biting.

And then just don’t wash his cover off!

I know it’s not ideal to have a horse that’s dirty from head to toe, but I’d rather forego cleaning my horses for a few days if it means they get a break from the hell-spawn that are horseflies.

Plus, mud will cover areas that the blankets won’t, such as the belly, inside of thighs, legs etc.

Of course, you’ll need to clean him if you need to put some kind of tack on for working, but if and when you can, just let nature take care of it and your horse will thank you for it.

You can also make sure that after every workout, your horse gets to renew his mud cover – though that doesn’t stop the horseflies from biting while you’re out riding.

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