Horse Flies Suddenly Appear In Homes: 3 Reasons Revealed

The worst type of fly that you can have inside your home is the horse flies. 

Horseflies are annoying and, for lack of a better word, dangerous. 

These files don’t show up all around the year. But there comes a time when horse flies suddenly appear in homes.

So, why do horse flies appear suddenly? When do horse flies show up? And what causes that occurrence?

This guide will answer these questions. And you’ll also find out ways to get rid of horse flies in your home and property. 

Plus, a lot more!

Keep reading.

What Are Horse Flies – An Introduction

Horse Fly Suddenly Appear

If there’s any fly that looks like a housefly and bites hard, it’s the horse fly. 

Horse flies are the most aggressive species of flies with sharp mouthparts that can tear the flesh of humans and animals.

And they move in swarms and clusters too. So, you don’t want to get in their way. 

Horseflies are active starting from late spring till late summer. You’re no stranger to horse flies if you live in a barn or farm with animals and live stocks. 

Horseflies got their name from their habit of attacking horses and feeding on their blood. But they’re not only limited to horses. Horseflies can feed on the blood of any mammal.

You’ll also come across horse flies during the summer if you live near water bodies. Campers and hikers get nasty bites from horse flies when they camp or station near rivers and lakes.

Horseflies are bigger than your average house flies. A fully matured adult horse fly grows up to 1.25 inches in length. 

Horseflies are black and have transparent wings with visible veins. Their eyes are also visible large and look purplish. 

But unlike other flies, horse flies’ antennae are small. You might not be able to spot the antennae when they’re stationary. 

Horse Fly Bite

Horseflies are biting flies with a sharp blade-like mouth that can rip open the flesh of humans and animals.

Horseflies feed on the blood of animals like your livestock in your farm and barn. 

Horseflies locate their prey by detecting the carbon dioxide they exhale. Experts have proved that dark and shiny moving things also attract horse flies.

Certain chemicals attract horseflies to cattle and horses. Acetone in cattle’s breath, ammonia in cattle urine, and octanol in cattle sweat draw horseflies to livestock. 

The interesting fact is that, like the mosquitoes, the female horse flies bite humans and animals. 

The male horseflies don’t bite humans and animals. They feed on the flower nectar and pollen.

Female horse flies need big blood meals to produce eggs. That’s why they bite livestock and humans living on farms multiple times. 

Horsefly bite is painful. As per medical news today, the bite wound is red and looks like a hive. The bitten area can also discharge pus if not treated at the right time. 

On cattle and horses, horse flies bites appear as open wound markings with blood spilling out of the wound. 

Now it’s clear that horse flies can bite you and your livestock if you’re living in a place where horse flies are common.

But why do horse flies appear in homes suddenly?

The following section answer the question

The 3 Reasons For Sudden Appearance Of Horse Flies In Homes

Horse fly appear in home all of a sudden

The three reasons for the sudden appearance of horse flies in your home are –

  1. There are livestock on your property
  2. Your home is emitting a pungent smell of ammonia
  3. Your property is enabling the breeding of horse flies.

Let’s get into each of them. 

Horseflies are not like house flies that would feed on the trash in homes and yards. 

They’re blood-sucking flies. And most of the time, they get their blood meals from humans and animals outdoors.

But horse flies can enter your home too. And that happens during the summer months. Another species of flies that suddenly show up in homes during the summer months are the cluster flies.

But cluster flies don’t bite.

So, how do horse flies get in the house?

Horseflies enter homes through open doors and windows, especially when you’ve things in and around your house that attract them.

Livestock is one of them. Plus, the air conditioner in your home discharges water that has ammonia in it. 

That ammonia causes a sour smell that attracts horse flies into your home. 

Detecting the scent of ammonia, the horse flies will get inside your home through the open doors, windows and through any gaps and cracks that they can find. 

Your property, yard, or garden can also be a breeding ground for horse flies. 

Female horse flies will lay eggs in compost piles, decaying organic matter like wood and leaves, pond shores, near swimming pools, and even in termite mounds.

The eggs hatch into predatory larvae. The larvae of horse flies feed on tiny invertebrates and, at times, on frogs too.

If there are damp conditions with many organic wastes on your property, horse flies will live and breed there. 

So, how to get rid of horse flies? And how to protect yourself from horse flies bites?

Let’s find it out

How To Get Rid Of Horse Flies In Your Home And Property?

There are three stages of horse fly elimination – examination, treatment, and prevention.

Let’s get into each of these stages.

But before carrying out these steps, please wear a PPE or Personal Protective Equipment kit. It’ll protect you from the bites of horse flies.

Examination or Inspecting For Horse Flies

In this step, you’ll determine the severity of the infestation and find out its source.

For that, you’d need to examine the sources of horse flies on your property.

Check for horse flies in places close to your livestock’s living places. The places where you store manure, where your livestock eat, compost piles, near pools, ponds, and pastures are where you can check for horse flies’ presence. 

Doing that will help you determine the size of their infestation and at what specific time of the day they’re most active. 

You’ll also be able to spot the larvae of horse flies in places like rotting wood piles, foliage, and compost mounds. 

You’ll also spot many grubs near any aquatic vegetation like bushes and shrubs growing around your swimming pool or pond.

Mark the areas where you’ve spotted horse flies. 

Then move on to the next step, which is treatment.

Treat Your Property To Get Rid Of Horse Flies

To get rid of horse flies, here are the things that you’ll need –

  1. Disposable Flytraps
  2. Equine spray for livestock
  3. Outdoor Insecticide Spray
  4. IGR (Insect Growth Regulator)

Now follow the six steps to use the above materials to get rid of horse flies.

Activate The Fly Trap And Keep It In Places Where You’ve Spotted Horse Flies

The flytrap is a great non-toxic way to trap horse flies.

To activate the trap, remove the plastic seal at the top. You’ll find a tab when you release the seal.

Pull the tab to break it. And then fill the trap with water till the brim. That’ll activate the flytrap.

You’d need to use multiple fly traps to keep in different places where you’ve noticed horse flies’ activities. 

These bags are disposable. When they’re full of horse flies, discard these fly traps.

Spray The Horse Fly Repellent Spray On Your Livestock

This step saves your livestock from the injuries and wounds that horse flies cause to your animals. 

Clean your livestock. Ensure that there’s no dirt and dust on your livestock. Then spray the horse flies repellent spray on the livestock’s skin.

Caution: Do not spray the horse fly repellent spray on livestock’s nose and eyes.

Mix Insecticide And IGR In A Spray Bottle

Now it’s time to go to the offensive against horse flies on your property.

Mix 4 teaspoons of insecticide with 4 ml of IGR (Insect Growth Regulator) in one gallon of water. One gallon of the mixture is sufficient for an area of 1000 sq. ft.

For large areas, you’d need to prepare more of this mixture. Or you can also go for fogging treatment by hiring a pest control professional.

Stir the mixture well and pour it into the insecticide spray bottle.

Then spray the mixture in every place where you observed the horse flies and their larvae.

Around your home, spray it on the windows, doors, mulch beds, and around your home’s foundation. 

Do not spray the mixture inside the home.

The flex 10-10 is an insecticide that will kill adult horse flies. The IGR (Insect Growth Regulator) targets the larvae to kill them and prevent them from growing into adult horse fly.

Inside your home, you can use any interior insecticide spray on the horse flies. But do not forget to repair your AC and fridge if they’re discharging too much water.

The water from appliances contains ammonia which attracts the horse flies to your home. 

Prevention Of Horse Fly Infestation In The Future

Now that you did your bit to get rid of horse flies, it’s time to ensure that they don’t come back. 

The prevention process will ensure that you and your livestock don’t get further bites from the horse flies. And the chances of the sudden appearance of horse flies inside your in the future is zero.

And the simplest way to do it is to use a granular fly bait around the perimeter of your property and your home’s foundation.

The granular fly bait is like paint. You paint your property’s perimeter and the perimeter of your barn where you keep your livestock.

Doing it is easy. Pour the granular fly bait into a bowl and add water. 

After adding water, the granular bait will turn into a paste. Take a paintbrush and apply it to the barn walls, fencing, and your home’s foundation. 

You can also paint your home’s window frames and door frames if horse flies are a big menace in your area.

The paint will repel horse flies from sneaking inside your home and barn and biting you and your livestock.

There are some highly effective preventive measures for horse flies.

  1. Installing window screens with fine mesh to prevent any type of bug, including horseflies, from entering your home
  2. Seal any gaps and cracks on your barn and in your home’s walls, doors, and windows. That’ll also stop the horse flies from sneaking inside your barn and house.
  3. Ensure the places where you store and process the manure is always covered by a tight lid.
  4. Don’t let livestock excrement gather in one place or be scattered around in your property for days.
  5. Have proper waste disposal for your property. Don’t let organic wastes pile up in places like where you feed your livestock and horses.
  6. The place where you keep your livestock feed should be clean.
  7. Don’t let foliage and organic wastes like rotting wood piles lie around in your property for days. 
  8. Prevent excessive dampness in your property by not overwatering and by not letting water get stagnant.

Are Horse Flies Territorial?

Horseflies are pretty territorial. They can attack you if you walk through their hiding or nesting places.

Are Horse Flies Venomous?

To a human, they’re not. But they can transmit swamp fever to horses which can be deadly for them.

Are Horse Flies Attracted To Water?

Yes, horse flies are attracted to water. That’s why they prefer to live near aquatic places like lakes and ponds.

In a residential area, horse flies can make their nests near swimming pools.

Are Horse Flies Attracted To Light?

Horseflies are attracted to linear polarized light, which is a reflection of light. They detect water by picking up the reflected light from the water’s surface.

Is Horse Flies Aggressive And Dangerous?

Yes, horse flies are aggressive flies, and they’re dangerous too. They can cut open the skin of animals and humans to suck their blood.

Can Horse Flies Bite?

Yes, horse flies bite. Horse flies have sharp mouthparts like a blade that they use to rip open the skin of their targets.

Do Horse Flies Sting?

No, unlike other stinging bees, horse flies don’t sting. They bite.

When Do Horse Flies Go Away?

Horseflies are summer pests. By the beginning of the fall, their numbers started to decrease.

Are Deer Flies And Horse Flies The Same Thing?

No, they’re not. There are significant differences between horse flies and deer flies.

Deer flies are smaller than horse flies. And when deer flies are stationary, their wings are quite far apart, making them look like a moth rather than fly.

Deer flies also have brownish-yellow straps on their abdomen, which is not there in horse flies. Horse flies’ abdomen is black. 

Deer Fly
Deer Fly

But both deer flies and horse flies bite by cutting the skin with their scissor-like mouthparts.

Bites of deer flies also cause rabbit fever. The symptoms of rabbit fever are skin ulcers, fever, and headache.

It’s always advisable to see a doctor if deer flies bite you.


The reasons for the sudden appearance of horse flies in homes are three –

  1. There are livestock on your property
  2. Your home is emitting a pungent smell of ammonia
  3. Your property is enabling the horse flies to breed.

Horseflies get active in summer, and they leave a painful bite on both humans and animals.

In this guide, you’ve learned why you get horse flies bites and how to get rid of horse flies on your property.

There’s also a list of preventive measures that you can take right now to stop horse fly infestation on your property in the future.

Remember, horse flies feed on your and your livestock’s blood to be alive. And if there are conditions in your barn or property supporting the horse flies, they’ll keep coming back.