House Fly vs Horse Fly
House Flies and horse flies are easy to mix up at a glance, but a few details separate them quickly. Here is how to tell which one you found and what, if anything, you should do about it.
Quick answer
Check for this first. A house fly has four dark lengthwise stripes on a gray thorax, while a horse fly has large, heavy body with very large, often iridescent eyes.
Side-by-side comparison
| House Fly | Horse Fly | |
|---|---|---|
| Group | Flies & Mosquitoes | Flies & Mosquitoes |
| Scientific name | Musca domestica | Tabanus spp. |
| Size | 6–7 mm | 10–30 mm |
| Colors | Gray and Black | Black, Brown and Gray |
| Legs | 6 legs | 6 legs |
| Wings | Yes | Yes |
| Bites or stings | No | Bites |
| Risk | Nuisance | Can bite or sting |
| Key feature | Four dark lengthwise stripes on a gray thorax | Large, heavy body with very large, often iridescent eyes |
Key differences
- Size: Horse Flies are larger, reaching 30 mm, while house flies top out around 7 mm.
- Color: House Flies are gray and black; horse flies are black, brown and gray.
- Risk: the house fly is a nuisance pest but not a health threat to most people, while the horse fly can bite or sting, usually with mild, local effects.
- Where found: look for house flies in the kitchen and indoors; horse flies turn up in yards and on patios, in woods and along trails and near water.
- Signature feature: House Flies: four dark lengthwise stripes on a gray thorax. Horse Flies: large, heavy body with very large, often iridescent eyes.
How to identify house flies
The most common fly in homes, a dull gray fly with four dark stripes on its thorax. It breeds in garbage, manure and rotting food and lands on nearly everything.
- Four dark lengthwise stripes on a gray thorax
- Red compound eyes
- Sponging mouthparts that cannot bite
How to identify horse flies
A large, stout fly with huge eyes that pursues people, horses and cattle for blood. Females slice skin with blade-like mouthparts, causing a sharp, painful bite.
- Large, heavy body with very large, often iridescent eyes
- Clear or dark-tinted wings held apart at rest
- Persistent circling around people near water
Which one is more dangerous?
The horse fly carries more risk. Horse fly bites are painful and can swell; they rarely transmit disease to people in the US.
House flies don't bite, but they can carry bacteria that cause food poisoning. Horse fly bites are painful and can swell; they rarely transmit disease to people in the US.
Where and when you'll see each
House Flies turn up in the kitchen and indoors, mostly in spring, summer and fall. Horse Flies turn up in yards and on patios, in woods and along trails and near water, mostly in summer.
Where you found the bug is itself a strong clue, since these two rarely share the same spots.
What to do if you find one
House Flies: Keep trash tightly covered and take it out often. Read the full removal guide for more.
Horse Flies: Wear light-colored long sleeves near ponds and pastures. Read the full removal guide for more.
Biology: flies & mosquitoes
Flies have only one pair of working wings; the second pair is reduced to small balancing knobs called halteres. They go through complete metamorphosis, and the larvae, called maggots, need moist organic material such as garbage, soil, drain film or standing water.
Frequently asked questions
What is the main difference between house flies and horse flies?
Size: Horse Flies are larger, reaching 30 mm, while house flies top out around 7 mm.
Which is bigger, a house fly or a horse fly?
House Fly: 6–7 mm. Horse Fly: 10–30 mm.
Do house flies or horse flies bite?
House Flies do not bite. Horse Flies can bite.
Where are they usually found?
House Flies: in the kitchen and indoors. Horse Flies: in yards and on patios, in woods and along trails and near water.