House fly vs Stable fly
These two are easy to mix up. Here's how to tell a house fly from a stable fly, and whether either one bites or stings.
House fly
Musca domestica
Stable fly
Stomoxys calcitrans
≠The key differences
Stable flies bite to blood-feed and have a prominent piercing proboscis; they hold their proboscis forward while feeding and the thorax lacks the same pattern of four stripes as clearly as house fly.
House flies do not have a rigid piercing proboscis and do not blood-feed; stable flies are biting and have a visible forward-pointing proboscis.
⚖︎Side by side
| House fly | Stable fly | |
|---|---|---|
| To humans | Disease vector | Painful bite |
| Size | 6-7 mm body length | 5-7 mm long |
| Colours | Gray, Dark gray / black, Yellow-gray, Reddish brown (eyes) | Gray, Dark brown, Black |
| Family | Muscidae | Muscidae |
| Habitat | Human dwellings, farm buildings, garbage dumps, compost piles, manure and other decaying organic material. | Farmyards, livestock bedding, decaying vegetation, damp compost, roadside vegetation and areas with mixed manure and organic matter |
| Range | Cosmopolitan — found worldwide wherever humans or domestic animals occur. | Cosmopolitan: found worldwide in temperate, subtropical and tropical regions where livestock and suitable breeding material occur |
| Active | Active year-round in warm climates; spring to autumn in temperate zones; mostly daytime (diurnal). | Warm months (spring to autumn in temperate regions), active in daylight especially mid-morning to late afternoon |
| Pest? | Yes | Yes |
🔍How to spot a house fly
- Gray thorax with four dark longitudinal stripes (more visible from above).
- Red-brown compound eyes (closer together in males) and slightly checkerboarded abdomen.
- Body length about 6-7 mm; sponging mouthparts and characteristic wing venation of Muscidae.
- Habit of resting on vertical surfaces and walking on food items while feeding with white saliva-like regurgitate sometimes visible.
🔍How to spot a stable fly
- Look for a 5-7 mm grayish fly with darker longitudinal thoracic markings and patterned abdomen.
- Check for a rigid, forward-pointing proboscis beneath the head used for piercing skin (visible in close photos) — unlike non-biting house flies.
- Observe behavior: stable flies actively bite and commonly rest on legs and lower body of livestock and humans, often repeatedly.
- Compare with house fly: stable flies are more robust, have piercing mouthparts and bite; house flies have sponge-like mouthparts and do not bite.
?Frequently asked questions
What is the difference between a house fly and a stable fly?
Stable flies bite to blood-feed and have a prominent piercing proboscis; they hold their proboscis forward while feeding and the thorax lacks the same pattern of four stripes as clearly as house fly. House flies do not have a rigid piercing proboscis and do not blood-feed; stable flies are biting and have a visible forward-pointing proboscis.
Is a house fly or a stable fly more dangerous?
House fly: Disease vector. Stable fly: Painful bite. House flies do not bite to feed, but they can contaminate food and surfaces with bacteria, protozoa and viruses picked up from waste and animal matter. Stable flies deliver painful, biting wounds while feeding on blood.
Identification from photos is never certain: don't handle insects you can't identify, and get medical advice for bites, stings or allergic reactions.