| Scientific name | Bradysia spp. |
|---|---|
| Group | Flies & Mosquitoes |
| Size | 2–4 mm (up to about 0.16 in) |
| Colors | Black and Gray |
| Legs | 6 legs |
| Wings | Yes |
| Where found | Indoors, anywhere |
| Most active | Spring, Summer, Fall and Winter |
| Bites | No |
| Stings | No |
| Risk level | Nuisance |
How to identify it
The fungus gnat is a tiny member of the flies & mosquitoes group. Only one pair of flying wings; the hind pair is reduced to tiny knobs. Check for these three features:
- Delicate dark body with long legs and antennae
- Weak, erratic flight near plants
- Y-shaped vein pattern in the wings
About this bug
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.
You'll usually find fungus gnats indoors. They are most active in spring, summer, fall and winter.
Is it dangerous?
Fungus gnats don't bite; larvae can damage seedlings and young roots.
Our rating: Nuisance, meaning it is a nuisance pest but not a health threat to most people.
When you'll see fungus gnats
Fungus Gnats are most active in spring, summer, fall and winter. In spring, overwintering adults become active and many species lay their first eggs. Summer heat speeds up development, so populations can grow quickly. In fall, many bugs look for shelter, and some move toward or into buildings. In winter, activity continues mainly indoors in heated spaces.
Typical places to check: indoors, anywhere.
About flies & mosquitoes
The fungus gnat is one of the 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.
Fly problems are almost always breeding-site problems. Finding and removing the moist material where larvae develop works far better than swatting adults.
What to do about it
- Let the top inch of potting soil dry out between waterings
- Use yellow sticky traps to catch adults
- Treat soil with Bti (mosquito bits) to kill larvae
Read the full guide: how to get rid of fungus gnats.
Bugs that look similar
Color: Fungus Gnats are black and gray; fruit flies are tan, brown and red.
Size: Mosquitoes are larger, reaching 6 mm, while fungus gnats top out around 4 mm.
Where found: look for fungus gnats indoors; drain flies turn up in the bathroom, in the kitchen and in basements and garages.
Frequently asked questions
What does a fungus gnat look like?
Delicate dark body with long legs and antennae. Adults measure 2–4 mm (up to about 0.16 in).
Does the fungus gnat bite or sting?
It does not bite. It does not sting. Fungus gnats don't bite; larvae can damage seedlings and young roots.
Where do fungus gnats live?
Fungus Gnats live indoors.
When are fungus gnats most active?
Mostly in spring, summer, fall and winter.