Four flies that bite your horse

Four Flies That Bite Your Horse

It’s that wonderful time of year when we all spend more time with our horses. The warmer weather has arrived and, sadly, so have the flies. "Biting flies", as they're known, are a real menace around horses as they irritate and harass them, often causing stress and anxiety. Here's some more information about the four worst offenders...


Where are horse flies found?

Anyone who has spent any time around horses knows about the worst offender of all – the horsefly (Tabinidae). These pesky pests appear as soon as the weather heats up – around June and thereafter until the weather gets cooler again. They are busiest on warmer, sultry days, and are commonly found around woodland or wet, marshy areas.

How to identify a horse fly

Horse flies are dark, almost black in colour with very large, prominent eyes that they use in hunting.

Horse Fly

What does a horse fly bite look like? 

Horse fly bites are nasty and come up like lumps with a characteristic ulcer-looking middle to them. Female horse flies actually cut through the skin with their knife-like mouth parts rather than pierce it. And this is why horses often become restless and unmanageable when they're bitten.

What's the best way to prevent my horse from being bitten?

The best way to avoid your horse having to cope with these symptoms is to keep him in during the day, when the horse flies are about. Horse flies don't like dark areas and will not follow a horse into a dark stable. If this isn't possible, cover your horse up well with a fly rug when he's out in his field. If he suffers particularly badly, also get a rug that you can ride in as well.  

Unfortunately, horse flies are resilient insects which means many home-made insect repellents don't work that well on them. However, if you can find anything that contains pyrethroids (Permethrin or Cypermethrin), this does work pretty well.


Where are black flies found?

In the summer, black flies (Simuliidae) can be a real problem for both horses and their riders. They are found mainly in mixed birch and juniper woodlands, and at lower levels in pine forests, moorlands, and pastures. They tend to feed in the daytime, normally when wind speeds are low.

How to identify a black fly

They are tiny little flies, around 2mm to 5mm in size, that breed really quickly in flowing water. Identifiable by their black or grey bodies, short legs and antennae, they're about the size of a small mosquito. However they're much more bulbous and darker than a mosquito.

What does a black fly bite look like? 

Black flies are really annoying and feed around a horse's face. They particularly like ears which can drive horses crazy. However, they also bite horse's necks and their bellies, leaving painful lumps which bleed and then scab over. This of course attracts more flies making the situation even worse.

Black Fly

What's the best way to prevent my horse from being bitten?

Synthetic pyrethroid fly spray is a good deterrent. However, physical barriers like ear nets or fly masks with ears work well. Check that fine mesh fabric is used for the ears otherwise the stable flies will get through the fabric. Another popular solution is oil of citronella. This puts the flies off landing on horses in the first place. Petroleum jelly (Vaseline) is another alternative which you can apply to the inside of your horse's ears to stop the flies from biting them. Make sure you do this very gently and remember some horses do not like their ears being touched!


Where are midges found?

Midges tend to make an appearance on damp and cloudy summer days. They are big fans of wet ground but they also love dense undergrowth along with dawn and dusk conditions. Stagnant water is their perfect breeding ground as they lay their eggs in the still water. 

How to identify a midge

Midges (Culicoides) are tiny flying nuisances that are only 1mm-3mm long. Grey in colour, often their wings are very hairy and patterned. When the midge is at rest, these wings will lie flat with one crossed over the other.


What does a midge bite look like? 

As midges are so small, you're more likely to feel the bite rather than see it. They bite various parts of a horse's body, but most commonly horses are seen to rub away both their manes and the tops of their tails, which can exacerbate sweet itch. Despite their tiny size, midge bites can be annoying and may even cause an allergic reaction.

What's the best way to prevent my horse from being bitten?

An effective way of keeping midges at bay is to use insect repellents that are ‘permethrin’ based and to apply them late in the afternoon.  Again, any oil-based product is good at preventing midges from biting.

Just as with black flies, fly rugs and fly masks with ears are another good method of avoiding bites by midges.


Where are stable flies found?

The manure and wet straw often found at livery yards provides the perfect breeding ground for stable flies. They lay their eggs in anything moist found around a yard, which is why it's so important to make stable hygiene such a high priority. Contrary to what their name suggests, they tend to prefer the outside environment to indoors, such as stables.

How to identify a stable fly

The stable fly is about 6 or 8 mm long with four distinct, dark longitudinal stripes on its body and several dark spots on the abdomen. It has sharp mouthparts protruding from the head.

Stable Fly

What does a stable fly bite look like? 

These flies feed around horse's legs and bellies where they bite, causing a lot of irritation and painful wheals which have scabs in the centre.

What's the best way to prevent my horse from being bitten?

The best way to prevent your horse from being bitten is to eliminate the conditions that attract stable flies to the yard. This means that everything needs to be kept as clean as possible.

However, hanging fly traps helps, and using a fly repellent containing ‘permethrin’ is also an effective deterrent. Spray your horse's legs carefully so that you don't spook him in the process. If he objects to the spray, then spray the repellent on a sponge and wipe the legs over with the repellent. Do this several times a day.

In summary...

We all love the summer - it's a wonderful time of year for both riders and horses. However, the eternal fly problem can turn a great day into a real disaster if you're not ready and able to cope with the situation. Being prepared with all the right repellents goes a long way when it comes to enjoying what is the best time of the equine year!

Look out for our other articles to help you cope with the flies over the Summer months…

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Kim Horton

Co-Founder of EQUUS and a keen equestrian, when Kim's not at her desk she's with her horse, Waldo.


  • Kate McArthur posted on June 07 2017 at 05:06 AM

    I found this article absolutely fascinating.Thankyou.I really had no idea so many variants.I now know why wasmgoing on with my boy,I found several round lumps on the middle of his undercarriage.Initially I worried some kind of internal issue brewing,then assumed horsefly,as they were the species that were the only ones to bite this way.He hasn’t had this problem before but I moved to a new place 6 months ago.I embraced the opportunity to by him a fab fly rug for the first time in his life with me,6years.Lovely zebra print one :) seems to be working very effectively.
    He is my first horse and I am 44 now and learning all the time.He is a trotter x tb.sadly he suffers with laminitis and on on occasion rotated the pedal bones.he is 100% now but I live life on the edge with the anxiety of one more episode.i can not let it happen to him again…ever!!If you have knowledge to share about laminitis,,I would love that and I believe you could broaden my knowledge everything I could find on the subject.would appreciate your input if you have any.He is 6 years old and has been tested by vets and negative.i hope to have him a long long time so permenat management for the rest of his life.Can you pass my info and advice on.thankyou..

  • Jacquie posted on June 07 2017 at 07:06 AM

    Hi. Do you know which fly repellants contain Permethrin or Cypermethrin?

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