Is It a Fly? How to Tell Flies From Look-Alikes
Flies: 4 marks to check, what they are often confused with, whether they bite or sting, and where they turn up, quoted from university entomology and IPM sources.
At a glance
- Group: Order Diptera (true flies)
- Body plan: Flies are distinguished from all other insects by having only one functional pair of wings (two wings total, versus four in bees/wasps). Mouthpart type varies by species (e.g., house flies have sponging mouthparts).
- Size: House flies are less than 3/8 inch (about 9.5 mm) long; size varies widely by species within the order (see crane fly and fruit fly notes below).
- Bites or stings: Most common house flies cannot bite (sponging mouthparts); some other fly species, such as stable flies, do bite and feed on blood.
- Where you find them: Fruit flies are common in homes, restaurants, supermarkets, and wherever food is allowed to rot or ferment; they breed in drains, garbage disposals, empty bottles/cans, trash containers, mops, and cleaning rags.
How to tell it is one of the flies
- Crane fly (often mistaken for a giant mosquito): distinguished from mosquitoes by larger size and by wings that lack the scales found on mosquito wings; it is a true fly with only two functional wings.
- Crane flies are harmless — many adults lack mouthparts entirely and they do not bite or sting people.
- Fruit fly (vinegar fly): tiny (~1/8 inch), tan front body with black rear, usually red eyes; found around rotting/fermenting food in kitchens, restaurants, and supermarkets.
- House flies cannot bite because of their sponging mouthparts, whereas some other flies (e.g., stable flies) do bite.
Often confused with
People most often mix flies up with:
Open the other page and compare its list against the marks above; the differences are usually in the antennae, wings or the way the body is divided.
Bites and stings
Most common house flies cannot bite (sponging mouthparts); some other fly species, such as stable flies, do bite and feed on blood. Seek medical care promptly for severe symptoms or any allergic reaction.
Where they turn up
Fruit flies are common in homes, restaurants, supermarkets, and wherever food is allowed to rot or ferment; they breed in drains, garbage disposals, empty bottles/cans, trash containers, mops, and cleaning rags.
How to photograph it for identification
Get as close as your camera will focus, from directly above, in daylight or a bright lamp. Include the whole body with the legs and antennae in frame; a second shot from the side shows wings and body segments. Put a coin or ruler next to it for scale. For a bite or a bug found on skin or bedding, photograph the bug itself, not the mark. The app names the likely group; use the list above to confirm.
FAQ
Do flies bite or sting?
Most common house flies cannot bite (sponging mouthparts); some other fly species, such as stable flies, do bite and feed on blood. Seek medical care promptly for severe symptoms or any sign of an allergic reaction.
What is the quickest way to recognize flies?
Crane fly (often mistaken for a giant mosquito): distinguished from mosquitoes by larger size and by wings that lack the scales found on mosquito wings; it is a true fly with only two functional wings.
How do I tell flies from mosquitoes?
House flies cannot bite because of their sponging mouthparts, whereas some other flies (e.g., stable flies) do bite. The Mosquitoes page lists its own marks.
Related
See what's really crawling, flying, and buzzing past.
Start with a single photo.
Sources
- https://ipm.ucanr.edu/home-and-landscape/flies/
- https://citybugs.tamu.edu/factsheets/household/flies-house/
- https://citybugs.tamu.edu/2016/03/15/crane-flies/
- https://entomology.mgcafe.uky.edu/ef621
Updated 2026-09-11.