Bryan McAllister’s personal reference notebook
July 30, 2026Short & citedBlog
Civic Viewpoint.
A quiet encyclopedia with a personal desk
Kept by Bryan McAllister — short guides, clear facts, and the Canadian angle when it matters.
Field Notes • Insects

Horse fly

Horse flies are large, blood-feeding flies in the family Tabanidae, known for the painful bites of females and their association with livestock and other mammals.

Updated July 30, 20261 min readCited sources

Horse flies are large, blood-feeding flies in the family Tabanidae. Known for painful bites from females, they are a common pest near wetlands and livestock in Canada.

What it is

Horse flies are robust flies with a painful bite, though only females feed on blood (needed for egg development). Males stick to nectar, plant sap, and honeydew. Larvae grow in wet soil or water, feeding on decaying matter or small prey.

Why it matters

Female horse flies cause painful bites to humans, livestock, and other mammals. Their persistent attacks stress animals, reduce grazing, and can transmit diseases. In Canada, they are a seasonal nuisance for farmers, cottagers, and anyone near wetlands.

Key details

Horse flies undergo complete metamorphosis: eggs laid near water, larvae develop in moist habitats for months to years, then pupate and emerge as adults. Activity peaks in warm months near lakes, ponds, and streams across Canada.

In short

  • Only female horse flies bite; males feed on nectar and plant sugars.
  • They need blood meals to produce eggs.
  • Larvae develop in wet habitats like pond edges and stream banks.
  • Their painful bites can stress livestock and annoy people.
Canadian angle

Horse flies are common across Canada, especially near wetlands, lakes, streams, and rural areas where livestock are kept. They are of interest to Canadian farmers, cottagers, and outdoor users because of their painful bites and seasonal activity.

Quick questions

What do horse flies eat?
Adults feed on nectar, plant sap, and honeydew. Females also take blood from mammals to get protein for egg development.
Do horse flies bite?
Yes, only female horse flies bite. They have strong mouthparts that cut the skin, causing a painful bite.
What is the life cycle of a horse fly?
Complete metamorphosis: egg, larva, pupa, adult. Eggs are laid near water, larvae develop in wet soil or water for months to years, then pupate and emerge as adults.

Sources

  1. Wikipedia — https://en.wikipedia.org/wiki/Tabanidae
    Supports: Adult horse flies feed on nectar and plant exudates; females have mouthparts strong enough to puncture skin.
  2. Purdue University Extension — https://extension.entm.purdue.edu/publichealth/insects/tabanid.html
    Supports: Adults feed on nectar, plant sap, and honeydew; larvae develop in water or saturated soil; adults emerge from late spring into summer.
  3. Government of Canada — https://www.canada.ca/en/environment-climate-change/services/species-risk-public-registry/publications/wild-species-2010/chapter-17.html
    Supports: Adult horse flies feed on nectar and honeydew; females lay eggs in masses over water or wet soil; larvae hatch and drop to the substrate below.
  4. North Carolina State University Extension — https://content.ces.ncsu.edu/horse-flies-and-deer-flies
    Supports: Female horse flies inflict painful bites; males do not bite; eggs are laid near water; larvae develop in water or wet soil; life cycle often takes one to three years.
  5. University of Kentucky — https://entomology.mgcafe.uky.edu/ef511
    Supports: Horse flies are bloodsucking insects; larvae develop in mud, wetlands, or seepage areas and may feed on decaying organic matter or small organisms.
  6. EcoSpark — https://www.ecospark.ca/horse-fly
    Supports: Horse flies undergo complete metamorphosis with egg, larval, pupal, and adult stages; larvae develop in wet habitats and pupae lead to adults.