Insect identifier · Biting flies
How to identify a Horse fly
Tabanus spp.
· Also called horsefly, tabanid, greenhead, horsefly bite, greenhead fly identification
Large, silent, painful daytime bites on legs and back — horse flies and coastal “greenheads.” They slash skin rather than probe like mosquitoes.
Silent, heavy, painful on legs and back. Coastal greenheads are horse flies with a beach reputation. They slash. A drop of blood is normal. Deer flies are smaller and head-focused. Stable flies look like house flies and hit ankles. Marsh beaches at peak tide are a clothing problem, not a cream-only problem.
What does a horse fly look like?
Stout, large flies with huge iridescent eyes. Greenheads are coastal salt-marsh horse flies of the Atlantic.
Horse fly (Tabanus spp.) is Large, 10–25 mm. Colors people notice: black, brown, gray, green. Field marks: Stout, large flies; Huge iridescent eyes; Silent, heavy flight; Painful bite on legs, back, or arms. It is found outdoor. If those marks are missing, open Deer fly, Stable fly before you force this name. Search phrases that belong on this page include what a horse fly looks like and horse fly identification.
Identification marks
- Stout, large flies
- Huge iridescent eyes
- Silent, heavy flight
- Painful bite on legs, back, or arms
Size: Large, 10–25 mm
Colors: black, brown, gray, green
Where: outdoor
What a typical horse fly bite looks like
Deep, immediately painful bite that may bleed. Swelling and bruise-like itch can follow. Daytime only.
People searching “horse fly bite identification” want the pattern, not a single anonymous bump. A deep, immediately painful bite that may bleed. Swelling and a bruise-like itch can follow. Immediate steps on this page: Wash well; Ice and balm; If you have a large local reaction, rest the limb and consider clinician advice. This species does bite or sting people. Fever, spreading redness, trouble breathing, or a child with many stings is professional care.
If you were bitten
- Wash well
- Ice and balm
- If you have a large local reaction, rest the limb and consider clinician advice
Horse fly vs Deer fly
Size and silence. Greenheads are coastal horse flies. Deer flies are smaller and head-focused. Stable flies look like house flies and hit ankles.
- Deer fly identification (Chrysops spp.)
- Stable fly identification (Stomoxys calcitrans)
- Gallinipper identification (Psorophora ciliata)
- Yellow fly identification (Chrysops atlanticus)
- Dragonfly identification (Anisoptera)
Range and season
Continent-wide in summer. Marsh beaches at peak greenhead tide are infamous.
Livestock country, marshes, and Atlantic salt-marsh beaches in summer.
Continent-wide. Coastal “greenheads” are infamous on Atlantic marshes.
Summer days
Common questions
What is a greenhead?
A coastal horse fly (often Tabanus nigrovittatus) of Atlantic salt marshes.
Why does it hurt so much?
Females slash skin with scissor-like mouthparts rather than probing like a mosquito.
Do they bite at night?
No. They are daytime hunters.
What is a greenhead fly?
A coastal horse fly, infamous on Atlantic marsh beaches.
Do horse flies carry disease to people in the U.S.?
They are mainly a painful-bite pest for people. Livestock disease is a separate veterinary topic.