Psychodidae
- 01Broad, hairy wings. Held like a roof over the body at rest.
- 02Fuzzy body. Covered in fine hairs, like a tiny moth.
- 03Dark eyes. Small, dark and rounded.
- 04Beaded antennae. Long, with a bead at each segment.
- Adult size
- About 1/16 to 3/16 in
- Color
- Gray to dark gray, fuzzy
- Breeds in
- Slime film inside drains, traps and overflows
- Seen
- Resting on bathroom and kitchen walls
- Fix
- Scrub out the drain film, not just pour cleaner
Figures: University of Kentucky, Small Flies, University of Minnesota Extension, Flies.
What does a drain fly look like?
Small, gray and fuzzy, like a miniature moth. The wings are broad, hairy and held over the body like a roof when resting. The antennae are long and beaded. They are weak fliers and tend to sit on walls, mirrors and tile near sinks, tubs and showers, making short hops when disturbed.
Where do they breed?
In the gelatinous film that builds up inside drains, traps, overflows, garbage disposals, floor drains, sump pits and condensate lines. The larvae feed on the bacteria, algae and organic matter in that film. A drain that is rarely used, like a guest bathroom or basement floor drain, is a common source.
What does a drain fly problem mean?
That a drain somewhere has enough buildup to support them. Occasionally it means more: a broken pipe under a slab or a sewage leak, where organic material collects out of reach.
How Graduate handles drain flies
Find the drain. We check every sink, tub, shower, floor drain and condensate line, and use tape or cup traps to confirm which one is producing.
Remove the film. Mechanical cleaning with a brush, followed by an enzyme or bacterial drain treatment, removes the larval habitat.
Look for hidden sources. If flies keep coming after the drains are clean, a broken line or leak may need a plumber. The fly control page explains the whole process.
Which fly is it?
Each fly points to a different breeding source. Tap one for its full profile.
- Size
- About 1/4 in
- Look
- Gray, four dark stripes on the thorax
- Breeds in
- Garbage, manure, food waste
- Seen
- Kitchens, dumpster areas, around trash
- Size
- 1/4 to 1/2 in
- Look
- Shiny metallic green, blue or copper
- Breeds in
- Dead animals, meat scraps, garbage
- Seen
- A sudden swarm often means a dead rodent in a wall
- Size
- 1/4 to 1/2 in
- Look
- Gray, three dark stripes, checkered abdomen
- Breeds in
- Carrion and decaying meat. Gives birth to live larvae
- Seen
- Near garbage, dumpsters, dead animals
- Size
- 3/8 to 1/2 in, larger than a house fly
- Look
- Dull gray, golden hairs on the thorax
- Breeds in
- Outdoors. Larvae live in earthworms
- Seen
- Sunny windows and attics, fall through spring
- Size
- 1/16 to 3/16 in
- Look
- Fuzzy, moth-like, wings held like a roof
- Breeds in
- Slime film inside drains and traps
- Seen
- Bathroom and kitchen walls near drains
- Size
- About 1/8 in
- Look
- Tan, bright red eyes
- Breeds in
- Fermenting fruit, spills, drains, recycling
- Seen
- Hovering over produce and trash
- Size
- 1/16 to 1/8 in
- Look
- Dark, humped back, runs in short bursts
- Breeds in
- Decaying matter, often a broken drain or sewer line under a slab
- Seen
- Bathrooms, basements, commercial kitchens
- Size
- 1/16 to 1/8 in
- Look
- Dark, slender, long legs and antennae
- Breeds in
- Wet potting soil and damp organic matter
- Seen
- Around houseplants and windows
Figures: University of Minnesota Extension, Flies, University of Kentucky, Small Flies, Penn State Extension, Cluster Flies.
Treatment for this pest is covered under Fly Control.
Common questions
Will pouring bleach down the drain kill them?
Rarely. Bleach runs past the slime film the larvae live in. The film has to be scrubbed or brushed out of the drain, trap, overflow and stopper.
How do I know which drain they are coming from?
Tape a clear cup or a piece of tape sticky side down over each drain overnight. The drain that catches flies is the source.
Do drain flies bite?
No. They are a nuisance and a sign of organic buildup, not a biting pest.
Why do they appear in a bathroom we rarely use?
Unused drains dry slowly and build up slime film without being flushed, which suits the larvae well.
How long does it take to get rid of them?
Once the film is scrubbed out, adults stop appearing within a week or two as the last ones die off.
Can they come from outside?
Rarely in large numbers. A steady population indoors means an indoor drain or leak is producing them.
Get in touch
Tell us what you are seeing
Four questions, answered by a person within one business day. If it is urgent, call: the line is answered at any hour.
Fly Control
Start with a free consultation
A consultation is a phone call with us about your problem. You tell us what you are seeing, where in the building, and how long it has been going on. We tell you what it most likely is, what is causing it, and what it will take to fix. Most routine work can be priced on that call.
There is no charge and no obligation. If we are not the right fit, we will say so before anyone books a visit.
Call (631) 212-9601Schedule an inspection
Answered at any hour.