Dog sitting in tall grass with tongue out. She is sitting behind a pile of bags in a meadow at McCormack Trail located in Hamilton, Ontario
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Which Flies Bite Dogs in Ontario?

Are you thinking of staying in a yurt, glamping, camping, doing a farm stay, or simply heading to a dog beach for the day in Ontario? Excluding winter camping, the annoying “Bzz! Bzz!” And “Ouch!” of insect bites are inevitable.

When we think of insect bites and harm, we think of protecting dogs from mosquitoes, tick bites, and heartworms. 

But there are some insects we tend to forget – biting flies. If you’ve ever kayaked or canoed on a quiet lake or visited a dog beach at a provincial park (like the Long Point Provincial Park’s dog beach) for a day trip, then you’ll know just how painfully annoying biting flies are!

In today’s post, we’re going to look at which flies bite dogs in Ontario and learn about their causes, symptoms, and treatment.

This post contains affiliate links to products. I may receive a commission for purchases made through some of the links on this post.

Please note that I am not a veterinarian nor am I an animal health care professional. This blog is not intended to be a substitute for professional veterinarian advice, diagnosis, or treatment. Always seek the advice of your veterinarian with any questions you may have regarding the condition and/or the safety of your dog.

Which Flies Bite Dogs in Ontario?

In Ontario, the most common flies that bite humans and dogs are:

  1. Black Flies
  2. Deer and Horse Flies
  3. Stable Flies

Here’s an infographic summarizing what each fly looks like, its peak season in Ontario, its peak active time in a day, and where its favourite target areas are on our pooch. 

Fly Bites on Dog Infographic. Infographic contains information about the three common types of biting flies in Ontario, their key physical characteristics, a description of how fly bites can appear on a dog.

1. Black Flies

In Ontario, there are 63 different species of black flies (fun fact – there are 1250+ species known worldwide!). 

Size and Description: Black flies are small – about 1 – 5 mm and come in varying shades of black, yellowish-orange, and brownish-grey. They are mostly found in moving water.

Peak Biting Season: Adults tend to emerge and female black flies actively bite between mid-May to late June. Black flies are most commonly found near seasonal creeks and other freshwater sources like rivers. 

Favourite Biting Time: Black flies tend to be most abundant on hot, humid, days.

Black Fly Bites on Dogs: Bites from a black fly typically appear as red rings or dots on the belly of your dog. Typically, your dog isn’t bothered by these bites and the redness will fade on its own without any treatment. 


2. Deer and Horse Flies

Size and Description: These large flies (10 – 30 mm) are most well-known to anyone who has ever ventured outside of urban areas in Ontario. 

If you’ve ever been bitten by a fly and it felt like it took a chunk of your skin, then chances are you were bit by large deer and horse flies. 

With their knife-like mouth parts, their bites slash the skin to draw blood. Like the black flies, only the female flies draw blood.

Peak Biting Season: Deer and horse flies are most abundant during the summer and are often found around swamps, marshes, or the fringes of woodland areas.

Favourite Biting Time: Most are active during the day. These flies rely on motion to feed.

Deer and Horsefly Bites on Dogs: If deer flies or horseflies swarm your dog, you’ll likely hear them yelp, and see them suddenly twist and snap at the air. These bites hurt! Horsefly bites on your dog can cause minor cuts or welts – most notably around the face, ears, and armpits. Some of the cuts may produce visible blood from the bite incisions but will typically clot in a few minutes. Scabs may remain over the next few days.

Did you know?
For any dog, 32° C /  89.6° F is considered too hot. At this temperature, your dog is prone to heat stroke, regardless of its breed or health. Learn more about when it’s too hot for a dog this summer!


3. Stable Flies

Size and Description: Closer in size to a house fly (5 – 8 mm), these annoying stable flies tend to go for the ankle and feet. Even worse – both the males and the females will bite for a meal! 

Much like their name, stable flies tend to hang around livestock stables. Their favourite breeding grounds are rotting hay, grasses, or straws – really anywhere with some degree of decaying matter. 

Paddlers and swimmers know these are persistent little buggers! Black flies can fly long distances too so chances are you’ll still see them around in the middle of a lake!

Peak Biting Season: Mid to late summer. Stable flies are found near wet, moist, decaying matter. 

Favourite Biting Time: Most are active during the day. These flies rely on motion to feed.

Stable Fly Bites on Dogs: While stable flies tend to feed on larger domesticated animals like cattle and horses, these flies will also take the opportunity to feast on your dog too. Stable flies tend to target dog ears. To get a full meal – these flies will bite 4-5 times to get a full meal. Similar to the deer or horse flies, you may notice small cuts and some visible blood. Scabs may remain over the next few days.

How do I keep flies off dogs?
Learn how to keep flies off your dog discover 6 different methods on how to protect your dog from fly bites.


Frequently Asked Questions

Most fly bites on dogs tend to fade on their own without much treatment. after 48 to 72 hours.

Treating horsefly or deer fly bites on dogs:

If your dog was bit by a horsefly or deer fly, then you may need to do some basic wound care first aid – wash with clean water and mild soap to keep them infection free. 

While the wounds are still open, it’s best to keep your dog indoors. If you’re planning on spending more time outside, or if your dog is going to go swimming with open wounds, you can protect the open wounds with a thin coat of petroleum jelly.

Much like our cuts too – be sure to regularly wash off the petroleum jelly and keep the open wounds clean to prevent infections. 

In most cases, you don’t need to see a veterinarian for fly bites – injuries or red welts will typically heal on their own.  

However, there are rare cases where, some dogs may experience allergic reactions, infections or other complications, so if you notice signs of:

  • Excessive itching
  • Oozing wounds
  • Vomiting
  • Seizures
  • Swelling
  • Wheezing or trouble breathing
  • Excessive drooling
  • Weakness
  • Diarrhea

Or if you’re just feeling extra precautious (or you aren’t sure if it’s a fly bite, a tick bite, or any other type of reaction) – don’t hesitate and book a trip to your vet!

Generally speaking, no fly bites, while irritating and uncomfortable, won’t make your dog sick. However, fly saliva might trigger an allergic response in some dogs, which can lead to itchy, swollen, and painful open wounds that can become infected.

If you see your dog in any state of discomfort – you can always book a trip to your vet!

Yes. Fly bites can cause bumps on dogs depending on what type of fly has bitten your dog.

Black fly bites will typically appear as red rings or dots on your dog.

Horsefly, deer fly, and stable fly bites on your dog can cause minor cuts or welts or small bumps on dogs.


Looking for more pet travel advice?
View all my pet travel advice blog posts here.

Additional Reading

Hopefully, this post has helped you learn more about fly bites on dogs. 

Here are some of the websites I referenced to learn more about fly bites on dogs if you’d like to learn more.

Happy reading!

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