Drain Fly vs Fungus Gnat
Drain Flies and fungus gnats 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 drain fly has fuzzy, gray, leaf-shaped wings held roof-like over the body, while a fungus gnat has delicate dark body with long legs and antennae.
Side-by-side comparison
| Drain Fly | Fungus Gnat | |
|---|---|---|
| Group | Flies & Mosquitoes | Flies & Mosquitoes |
| Scientific name | Clogmia albipunctata | Bradysia spp. |
| Size | 2–5 mm | 2–4 mm |
| Colors | Gray and Black | Black and Gray |
| Legs | 6 legs | 6 legs |
| Wings | Yes | Yes |
| Bites or stings | No | No |
| Risk | Nuisance | Nuisance |
| Key feature | Fuzzy, gray, leaf-shaped wings held roof-like over the body | Delicate dark body with long legs and antennae |
Key differences
- Where found: look for drain flies in the bathroom, in the kitchen and in basements and garages; fungus gnats turn up indoors.
- Signature feature: Drain Flies: fuzzy, gray, leaf-shaped wings held roof-like over the body. Fungus Gnats: delicate dark body with long legs and antennae.
How to identify drain flies
A small, fuzzy, moth-like fly that rests on bathroom walls near sinks, tubs and floor drains. Its larvae live in the slimy film inside drains.
- Fuzzy, gray, leaf-shaped wings held roof-like over the body
- Short, weak, hopping flight
- Found near drains, especially in bathrooms
How to identify fungus gnats
A tiny, dark, mosquito-like fly that hovers around houseplants and windows. Its larvae live in moist potting soil and feed on fungi and roots.
- Delicate dark body with long legs and antennae
- Weak, erratic flight near plants
- Y-shaped vein pattern in the wings
Which one is more dangerous?
Neither is more dangerous than the other; both are rated nuisance on our scale.
Drain flies don't bite and aren't known to spread disease in homes. Fungus gnats don't bite; larvae can damage seedlings and young roots.
Where and when you'll see each
Drain Flies turn up in the bathroom, in the kitchen and in basements and garages, mostly in spring, summer, fall and winter. Fungus Gnats turn up indoors, mostly in spring, summer, fall and winter.
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
Drain Flies: Scrub drains with a stiff brush to remove the organic film. Read the full removal guide for more.
Fungus Gnats: Let the top inch of potting soil dry out between waterings. 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 drain flies and fungus gnats?
Where found: look for drain flies in the bathroom, in the kitchen and in basements and garages; fungus gnats turn up indoors.
Which is bigger, a drain fly or a fungus gnat?
Drain Fly: 2–5 mm. Fungus Gnat: 2–4 mm.
Do drain flies or fungus gnats bite?
Drain Flies do not bite. Fungus Gnats do not bite.
Where are they usually found?
Drain Flies: in the bathroom, in the kitchen and in basements and garages. Fungus Gnats: indoors.