Types of Flies in a Bar: How to Tell Them Apart by Location
Quick Answer: Match the fly to where you find it. Over a drain, a drain fly: about 1/8 inch, fuzzy and moth-like. Around fruit, bottle necks and sticky spills, a fruit fly with red eyes. Running rather than flying near bins, cracks and under equipment, a phorid fly. Near a potted plant, a fungus gnat. By the back door and bins, a house fly.
Different flies breed in different places, so the fix starts with naming the fly. Extension services in Texas and Oregon (checked October 2026) group the small flies found in food areas into four types and add the house fly as the main one that comes in from outside. The extension guidance is written for school kitchens, not bars, but the flies and their breeding sites are the same ones a bar meets. Our guide to fruit gnats versus fruit flies compares the three most confused.
How do you tell which fly is in your bar?
Look at where you see it, then at its size and how it moves. Sizes differ a little between sources, so the table gives each range as published.
| Where you see it | Fly | Size and look | Where it breeds |
|---|---|---|---|
| Over or near a sink or floor drain | Drain fly | About 1/8 inch (Texas A&M); 2 to 4 mm (Oregon State). Fuzzy, moth-like, weak flier | The slimy film inside drains, in grease traps, in condensate pans with algae |
| Around fruit, bottle necks, syrup and sticky bar tops | Fruit fly | Up to 1/8 inch (Texas A&M); 1 to 3 mm, red eyes (Oregon State) | Fermenting fruit and liquids such as liquor, syrup, soda and vinegar |
| Running across floors and walls, near garbage and under equipment | Phorid fly | 2 to 3 mm, dark brown, humped back (Oregon State). Runs rather than flies | Drains, damp waste, rotting food, garbage, cracks in floors |
| Near a potted plant | Fungus gnat | About 1/8 inch (Texas A&M); about 3 mm (Oregon State). Long-legged, mosquito-like | Moist soil of over-watered plants |
| At the back door, bins and outside | House fly | About 1/4 inch, 6 to 8 mm (Oregon State) | Mostly outdoors in garbage and decaying matter |
Which small flies breed inside the bar?
Drain flies, fruit flies, phorid flies and fungus gnats. Oregon State Extension (PNW 769) says the smaller flies that infest kitchens include these four, while most larger flies, such as house flies, invade from outdoors. It also lists "bar flies" among the common names for fruit flies in its sister publication (PNW 770). Texas A&M AgriLife Extension (IPM Action Plan for Small Flies) says fruit flies are attracted to liquor, syrup, soda pop and vinegar as well as ripening or rotting fruit, and that an egg can become an adult in under a week. To see where the fruit-fly side starts, read where bar fruit flies come from.
What does each fly point to?
The breeding site. Texas A&M says drain fly infestations could indicate a cracked or damaged sewer pipe or a dry drain trap, and that a persistent phorid fly problem can follow a broken underground sewage line. Fruit flies in large numbers may indicate spilled or spoiled fruit, poorly maintained garbage containers, buildup around drains, grout or broken tiles, and wet areas under and behind equipment. House flies point to open doors and bins. For the drain case, see fruit flies and bar sink drains. For house flies, see house flies in a bar.
Are these flies a hygiene matter or just a nuisance?
A hygiene matter. Texas A&M calls the four small flies capable of carrying disease-causing organisms, and Oregon State says house flies can carry germs from garbage to food-preparation surfaces. The FDA Food Code 2026 (section 6-501.111) requires the premises to be kept free of insects, by routinely inspecting for pests, using trapping or other control methods where pests are found, and eliminating harborage. It is a model code, and your health department's adopted version binds the bar.
Does a screen pourer help with any of them?
Only with the fruit-fly row, and only at the mouth of an open bottle. Esatto makes and sells the Esatto Liquor Pourer with Screen, 12 Pack. It is our own product, not an independent pick. Its collection page describes a free-flow pourer with a built-in screen that keeps bugs and debris out of your liquor. A screen does nothing for a drain, a bin or a phorid colony. Sanitation comes first, and the screen pourers collection lists the pack sizes.
Frequently asked questions
What types of flies are found in a bar?
Fruit flies, drain flies, phorid flies, fungus gnats if there are plants, and house flies from outside. Extension sources group the first four as the common small flies of food areas.
What are the little flies around my bar drain?
Probably drain flies: fuzzy, moth-like and about 1/8 inch. They breed in the film inside drains. A clear tape or cup over the drain overnight will show if they come from it.
What are the small flies near my bar fruit?
Fruit flies, which have red eyes and are drawn to ripening fruit and fermenting liquids. Check the fruit bin, bottle necks and sticky spills.
What is a phorid fly?
A small dark brown fly with a humped back that runs across surfaces rather than flying. It breeds in drains, damp waste and garbage, and under kitchen equipment.
Are drain flies and fruit flies the same?
No. A drain fly is fuzzy and moth-like and breeds in drain film. A fruit fly has red eyes and breeds in fermenting food and drink. The fix differs for each.
Is a gnat a type of fly?
"Gnat" is an everyday word for a small fly, not a species, and several of the flies above are gnat-sized. Texas A&M calls the adult fruit fly "gnat-sized".