The Canadian Encyclopedia — neutral, cited, updated
September 10, 2026Sources cited
Canadianwire.
Canada’s encyclopedia & explainer
HomeScience & NatureInsectBlack flies
Science & Nature • Insect

Black flies

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

By Ethan Anderson| Reviewed by Olivia Bennett, Standards & Fact-Checking Lead| Updated September 10, 2026|2 min read| Fact-checked

Black flies are small biting flies in the family Simuliidae, a group of true flies in the order Diptera. They are known by several common names, including buffalo gnats and turkey gnats. In Canada, more than 160 species are recorded, and they are familiar nuisance insects across much of the country.

Classification and naming

Black flies belong to the family Simuliidae in the order Diptera. Common names vary by region and include buffalo gnats and turkey gnats.

Physical characteristics

These insects are usually small, dark, and hump-backed, with short antennae and broad wings. Species vary in colour, including black, brown, grey, and yellowish tones.

Life cycle and habitat

Black fly larvae and pupae develop in running water, especially clean streams and rivers. Adults emerge to mate, and females of blood-feeding species use blood meals to support egg development.

Human and animal impact

Black flies are important nuisance pests because they bite humans and many animals, including livestock and birds. Their bites can cause pain, swelling, and itching.

Key facts

  • Black flies are true flies in the family Simuliidae.
  • They are small, hump-backed insects and are often dark in colour.
  • Adult males generally feed on nectar, while females of many species bite for blood before laying eggs.
  • Their larvae typically develop in flowing freshwater such as streams and rivers.
  • Black flies are widespread in Canada and are well known as biting pests.
🍁
Canadian context

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.

Frequently asked questions

What are black flies?
Black flies are small biting flies in the family Simuliidae, within the order Diptera.
Why are they called buffalo gnats?
They are often called buffalo gnats because of their hump-backed appearance.
Where do black flies breed?
They breed in running water, especially streams and rivers with flowing, oxygen-rich water.
Do all black flies bite humans?
No. Only females of blood-feeding species bite, and some species feed on other animals rather than humans.
Are black flies found in Canada?
Yes. Canada has more than 160 recorded species, and black flies are common nuisance insects in many regions.
Do black flies spread disease in North America?
They are not known to spread disease to humans in North America, although some species can transmit parasites in other regions.

References

  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.