Mosquitoes and Black Flies

MosquitoSpring is the season for biting insects such as black flies and mosquitoes in Algonquin Park. Each species of biting insect has a relatively short flight time and prefers specific hosts upon which to feed, with very few species actually preferring to bite humans. The graphics below indicate the typical flight time, in weeks, for biting insects in Algonquin Park. The darker colour indicates a greater abundance of the insects.

Tolerance to biting insects varies between visitors. If you are unsure about your tolerance for black flies and mosquitoes, for example, and will be visiting during their flight period, come prepared by packing your bug jacket and/or insect repellent, and you will have a great trip! Also see below for additional ways to prepare for "bug season" in Algonquin Park.

What to Expect and When

Black Flies

Black FlyCanada is home to 161 species of black flies that have different life cycles, with the majority flying as adults during the spring. In Algonquin Park, 42 species of black flies have been recorded, with just 4 species biting humans. Most species of black flies fly as adults from mid-May (depends on the weather in any given year) until late June, primarily during the day. The majority of black fly species in Algonquin Park feed upon birds and do not bite humans. Black flies develop in moving water and then emerge to fly as adults, with only the females requiring a blood meal Black Fly Flight Period and Abundance in Algonquin Parkto develop eggs. Females bite thin skin areas and will often land and crawl for some distance before biting. Black flies cut and rupture the skin and then soak up the blood. Irritation from the black fly's saliva can also cause swelling and itching in some people. Black flies seem to be most abundant on hot, humid spring days but are typically common throughout this mid-May to late June flight period. Covering up with clothing, such as a bug jacket, and applying insect repellent, as directed, offers some deterrent to the biting of black flies.


MosquitoCanada is home to over 80 species of mosquitoes with 67 species occuring in Ontario. Mosquitoes are abundant, beginning in mid to late May and lasting longer than black flies (usually into July depending upon the weather). Mosquitoes start their life as eggs that can sit dormant for many years before hatching under ideal conditions. Eggs are usually placed in calm water, such as beaver ponds, with larvae living just below the water's surface. Adults emerge from the water in late May to late summer, depending upon the species, with females searching out blood meals for development of their eggs. Mosquitoes are attracted to heat and carbon dioxide from exhaling and also through visual cues. Females land on hosts and use needle-like mouth parts to Mosquito Flight Period and Abundance in Algonquin Parkpierce the skin and suck in a blood meal. Females require several blood meals to acquire enough protein to produce a batch of eggs. Mosquitoes are abundant at certain times of the year and most abundant in cooler, shady parts of the forest, as well as in the evening and into the first couple of hours of darkness. These biting insects become less abundant through the night, although they do not disappear entirely. Covering up with clothing, such as a bug jacket, and applying insect repellent, as directed, offers good protection from the bite of mosquitoes.

Deer and Horse Flies

Horse FlyDeer flies and horse flies appear similar to large house flies, but they pack a strong bite. Unlike the sucking mouth parts of a mosquito, these insects have biting mouth parts that occasionally feel like they are "taking a chunk of skin" as a meal.Deer Fly and Horse Fly Flight Period and Abundance in Algonquin Park Horse flies are relatively larger and darkly coloured, while deer flies are smaller and have colourful eyes and dark-patterned wings. Deer and horse flies are most abundant during the summer months and fly only during the day. Being visual feeders attracted to motion, these insects circle humans waiting for a good time to land and obtain a meal. Insect repellent is less effective against deer and horse flies than compared to other biting insect species. Covering your head, arms, and legs is a good way to deter the bites from these insects.

Stable Flies

Stable FlyStable flies are smaller than deer or horse flies, about the size of a house fly. This species is often noticed by those paddling canoes, as these insects seem to prefer to bite exposed skin on ankles and feet. Originally believed to be Stable Fly Flight Period and Abundance in Algonquin Parkfrom Europe, these insects have biting mouth parts similar to horse and deer flies. Stable flies are in low abundance in Algonquin Park and only fly during the day.

Biting Midges (No-See-Ums)

Biting midges, also known as no-see-ums or sandflies, measure 1 to 4 mm in length and are nearly invisible to humans. Females require a blood meal for reproduction and can bite humans, leaving a burning sensation on the skin and irritation from the human body's reaction to the protein in their saliva. Biting midges can be active day or night and are most often discovered by those with small holes in their tents or RVs. Many tents feature no-see-um proof insect screening to deter entry of these insects. Biting midges are generally low in abundance in Algonquin Park during the summer months. Localized hot-spots can occur on warm, calm summer nights.

How to Prepare Yourself

  • Bug JacketKnow the traits of the insects you may encounter at certain times of the year.
  • Know your tolerance for biting insects, including your reaction to bites of certain species. If you are new to biting insects, cover up and use insect repellent if suitable.
  • Cover up. Wear long-sleeved shirts (if it is hot, lightweight shirts are good) with cuffs and collars that can be buttoned tight, as well as long pants with elastic cuffs (or tuck your pants into your socks). Some insects such as black flies will land on you and then crawl under clothing if they can. Wear light-coloured clothing (white, tan, khaki, etc.). Some insects such as black flies are attracted to dark colours.
  • Wear a bug jacket or bug hat available at local sporting goods retailers. Pick a model with good visibility and fine insect netting.
  • Sample Insect RepellentsUse insect repellent, as directed, when outdoors. See the latest insect repellent product safety guidelines from the Government of Canada and read the directions on your insect repellent.
  • When camping, set up a screen dining shelter to avoid biting insects.
  • Inspect your insect netting on your tent, RV, bug jacket, etc. prior to your trip. Repair or replace if necessary.
  • Keep up to date on the latest health information regarding biting insects (see below).

Diseases and Biting Insects

Mosquito-borne diseases such as Zika, West Nile, Malaria, Chikungunya, Yellow Fever, Dengue, and others are not known to occur in Algonquin Park. West Nile virus is established in Ontario, but not known from Algonquin Park. For more information see the Government of Canada for the latest information.

Related Information


Reserve your developed or backcountry campsite for your next visit.

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Special regulations for Algonquin's special fishery.