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July 30, 2026Short & citedBlog
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Field Notes • Insect

Black flies

Black flies are small biting flies in the family Simuliidae, a group of true flies in the order Diptera.

Updated July 30, 20261 min readCited sources

Black flies are small biting insects in the family Simuliidae. They are a familiar nuisance across Canada, especially near streams and rivers.

What it is

Black flies are true flies (order Diptera) and are also called buffalo gnats or turkey gnats. They are typically small, dark, and hump-backed, with adults ranging from 1 to 5 mm in length. Males feed on nectar; females of many species need a blood meal to develop eggs.

Why it matters

These flies are important biting pests in Canada, affecting humans, livestock, and birds. Their bites can cause pain, swelling, and intense itching. Although they are not known to transmit disease to humans in North America, they are a significant public-health and pest-management concern.

Key details

More than 160 species of black fly are found in Canada. Larvae and pupae develop in clean, fast-running water, such as streams and rivers. Adult females are the ones that bite, and only certain species target humans. Their presence peaks in late spring and early summer.

In short

  • Black flies are small biting flies in the family Simuliidae.
  • Only females bite; they need blood for egg development.
  • Larvae live in clean, flowing water.
  • Over 160 species are found in Canada.
Canadian angle

Black flies are a familiar nuisance insect across much of Canada, with more than 160 species recorded. They are especially associated with rural, wooded, and streamside areas, and they are part of Canadian public-health and pest-management discussions.

Quick questions

What are black flies?
They are small biting flies in the family Simuliidae, within the order Diptera.
Where do black flies breed?
They breed in running water, especially streams and rivers with oxygen-rich flow.
Do black flies spread disease in North America?
They are not known to spread disease to humans in North America, though some species can transmit parasites elsewhere.

Sources

  1. Wikipediahttps://en.wikipedia.org/wiki/Black_fly
    Supports: Family Simuliidae, common names, and worldwide species count.
  2. Government of Canadahttps://www.canada.ca/en/environment-climate-change/services/species-risk-public-registry/publications/wild-species-2010/chapter-16.html
    Supports: Canadian classification, physical description, and number of species known in Canada.
  3. Orkin Canadahttps://www.orkincanada.ca/pests/flies/black-flies/
    Supports: Presence of more than 160 species in Canada and nuisance-pest status.
  4. University of Maine Cooperative Extensionhttps://extension.umaine.edu/home-and-garden-ipm/fact-sheets/common-name-listing/black-flies/
    Supports: Female biting behaviour, nectar-feeding males, and breeding in running water.
  5. University of Minnesota Extensionhttps://extension.umn.edu/outdoor-biting-insects-and-insect-relatives/black-flies
    Supports: Biting behaviour, activity patterns, and lack of known disease spread in Minnesota/North America.
  6. Spokane Regional Health Districthttps://srhd.org/health-topics/environmental-health/black-flies
    Supports: Size, biting behaviour, habitat near running rivers and streams, and bite effects.