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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.

By Ethan Anderson| Reviewed by Olivia Bennett, Standards & Fact-Checking Lead| Updated July 26, 2026|2 min read| Fact-checked

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. Adults usually feed on nectar and plant sugars, while females also take blood meals needed for egg development. Their larvae develop in wet or moist habitats and undergo complete metamorphosis.

Description

Horse flies are robust flies in the family Tabanidae. They are most notable for the blood-feeding behaviour of females and their strong association with large mammals.

Feeding

Adults of both sexes feed on sugars from nectar, plant sap, or honeydew, but females of many species also require blood to develop eggs. Larvae feed in wet habitats on decaying organic matter, small organisms, or other prey.

Life cycle

Horse flies develop through complete metamorphosis. Eggs are laid in masses on vegetation or objects over water or wet soil, larvae hatch and move into moist substrates, then pupate before emerging as adults. The larval stage may take one to three years to mature.

Human and animal impact

Female horse flies inflict painful bites on people and animals, especially livestock. Their bites can be a nuisance and, in some cases, may contribute to disease transmission. The repeated biting can also stress livestock.

Key facts

  • Adult horse flies feed primarily on sugars from nectar, plant sap, and honeydew.
  • Female horse flies of many species bite mammals to obtain blood for egg production.
  • Males do not bite and typically feed only on plant sugars.
  • Horse flies undergo complete metamorphosis with four life stages: egg, larva, pupa, and adult.
  • Female bites can be painful and horse flies may annoy or harm livestock and humans.
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Canadian context

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.

Frequently asked questions

What do horse flies eat?
Adults mainly feed on nectar, plant sap, and honeydew. Females of many species also drink blood to obtain protein for egg development, while larvae feed in wet habitats on decaying matter or small organisms.
How to repel horse flies?
Physical barriers such as screens, protective clothing, and avoiding peak activity near wet habitats are commonly used. Standard insect repellents may help reduce bites, but control is often difficult because horse flies are strong fliers.
Do horse flies bite?
Yes. Female horse flies bite animals and humans to obtain a blood meal. Males do not bite.
Are horse flies dangerous?
They are mainly a painful nuisance, but their bites can irritate skin and may contribute to disease transmission in some settings. They can also stress livestock through repeated biting.
What is the life cycle of a horse fly?
Horse flies undergo complete metamorphosis: egg, larva, pupa, and adult. Eggs are laid near water or wet soil, larvae develop in moist habitats for months to years, and pupae emerge as adults.

References

  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.