Life Cycle of Drain Flies: Understanding & Managing the Pesky Intruders

Drain flies, also known as moth flies or Psychoda spp., are tiny pests commonly found in and around drains, sewers, and other damp environments. Their life cycle goes through four stages: egg, larva, pupa, and adult, typically completing in 21 to 27 days, although higher temperatures can accelerate this process [^1^].

These insects are particularly notable for their ability to thrive in polluted, shallow water or highly moist organic solids where they feed on decaying organic material. In homes, adult drain flies can often be seen on walls or near drains, indicating an issue with excess moisture or buildup in plumbing systems [^2^]. Understanding their life cycle can help in controlling and preventing infestations effectively.

Life Cycle of Drain Flies

Egg Stage

Drain flies lay their eggs in clusters on moist surfaces, usually near drains and other damp areas. A female drain fly can lay around 30-100 eggs at a time. These eggs hatch within 32 to 48 hours, releasing the larvae.

Larval Stage

The larvae are worm-like, living in the gelatinous film found in drains, feeding on organic matter such as algae, bacteria, and fungi. They undergo a series of molts, typically taking 10 to 15 days to complete this stage. Larval stages are important for breaking down organic waste in drains.

Characteristics of Larvae:

  • Worm-like appearance
  • Live in gelatinous films in drains
  • Feed on organic matter

Pupal Stage

Once the larvae mature, they form pupae, a non-feeding stage in which they undergo metamorphosis. Pupation occurs near the larval feeding site, and this stage may take 3 to 4 days to complete.

Adult Stage

Once the pupal stage is completed, adult drain flies emerge. These adults are small, fuzzy, and gray to black in color. They do not bite and may live for around 2 to 27 days depending on environmental conditions. Adult drain flies are primarily a nuisance due to their presence in homes and buildings.

Characteristics of Adult Drain Flies:

  • Small (1/16 to 1/4 inch long)
  • Fuzzy, moth-like appearance
  • Non-biting insects
  • Attracted to moist areas near drains

In conclusion, the life cycle of a drain fly comprises of four stages: Egg, Larval, Pupal, and Adult. The entire process, from egg to adult, can take anywhere from 21 to 27 days. Drain flies are not harmful but can be a nuisance in homes and buildings.

Habitat and Breeding Conditions

Drains and Pipes

Drain flies, also known as moth flies or Psychodidae, primarily breed in the muck, slime, or gelatinous film often found in drains and pipes. This environment provides:

  • Ample moisture
  • Organic matter for feeding

Examples of common breeding sites in drains and pipes include:

  • Kitchen sinks, where food debris accumulates
  • Bathroom sinks, with accumulated hair, soap scum, and toothpaste

Bathrooms and Kitchens

Bathrooms and kitchens provide ideal habitats for drain flies due to the presence of:

  • Standing water in sinks and floor drains
  • High moisture levels

Preventing infestations in these areas involves:

  • Regularly cleaning and maintaining drains
  • Ensuring proper ventilation to reduce moisture

Standing Water and Sewage

Drain flies also breed in polluted standing water and moist organic solids like sewage. Breeding sites can include:

  • Sewage filtration tanks and septic tanks
  • Dirty garbage containers
  • Rain barrels
  • Tree holes with collected water
  • Moist compost piles
Habitat Drain Flies Fruit Flies
Drains, pipes, and slime Yes No
Bathrooms and kitchens Yes Yes
Standing water and sewage Yes No

Compared to fruit flies, moth flies tend to focus on damp, organic matter rather than ripened fruits, emphasizing the importance of maintaining clean and dry environments.


Control and Prevention Methods

Cleaning and Home Maintenance

To prevent drain flies, it’s essential to keep drains clean and moist areas dry:

  • Remove gelatinous film in drains by using a metal pipe brush
  • Regularly pour boiling water down drains to dissolve organic material
  • Clean kitchens and bathrooms thoroughly to eliminate breeding grounds
  • Repair leaks and ensure proper ventilation to reduce wet areas

For example, clean your shower drain weekly with a pipe brush and boiling water.

Biological and Chemical Control

Biological and chemical control methods target drain fly larvae and microorganisms in the drains:

  • Introduce beneficial microorganisms to break down decaying organic matter
  • Use chemical agents specifically designed for drain fly control


  • Effectively eliminate larvae and breeding sites
  • Reduce the need for frequent cleaning


  • Require proper identification of infested areas
  • Some chemicals may harm beneficial microorganisms

Traps and Lights

Traps and lights attract adult drain flies, sewer flies, and sewer gnats:

  • Sticky traps near drains and breeding sites
  • UV light traps attract and eliminate adult flies

Comparison Table

Method Pros Cons
Sticky Traps Effective at trapping adult flies Require regular replacement
UV Light Traps Attract a broad range of flying insects May not target larvae in drains

Use sticky traps in bathrooms and kitchens, and place UV light traps in basements or other infested areas.

Impact on Human Health and Environment

Allergies and Asthma

Drain flies, specifically adult drain flies, can contribute to allergies and asthma in sensitive individuals. Their presence can become a nuisance and may trigger allergic reactions in some people. For example:

  • Exposure to drain fly hairs or body parts.
  • Inhaling dust or debris from their breeding sites.

To reduce the risk of allergies and asthma, it is essential to maintain clean drains and control the drain fly population.

Disease Transmission

It is important to note that drain flies are not known to transmit diseases to humans. However, they can potentially carry bacteria from their breeding sites, typically moist and decaying organic matter, to other surfaces in homes or buildings. Some examples of surfaces they can come into contact with include:

  • Counter tops.
  • Sinks.

This means it is important to maintain proper sanitation to prevent any potential health risks.

Ecological Role

In the environment, drain flies play a vital role in breaking down organic matter. They are mostly harmless insects and are part of the insect order Diptera, family Psychodidae, subfamily Psychodinae. Their geographical distribution spans across North America, Europe, South America, and countries like Spain and Brazil. The larvae of these flies feed on decaying organic material, converting waste into simpler compounds that other organisms can utilize.

While they do play an essential ecological role, drain flies can be a temporary problem in homes or buildings during specific periods, such as winter or when windows are closed.

To mitigate drain fly infestation, consider the following control methods:

  • Regularly clean drains using a brush or enzyme-based cleaner, avoiding harsh chemicals like bleach.
  • Repair any leaks or drainage issues.
  • Seal cracks or gaps in walls and windows.

In conclusion, drain flies are a natural part of the environment, and while they can contribute to allergies or asthma in certain individuals, they do not pose a significant threat to human health. Proper sanitation and timely control measures can effectively manage drain fly populations and maintain a healthy living environment.

Reader Emails

Over the years, our website, has received hundreds of letters and some interesting images asking us about these insects. Scroll down to have a look at some of them.

Letter 1 – Bathroom Fly Larva


December 22, 2009
We’ve started seeing a number of these critters in our bathtub. They are 3-5 mm in length and are extremely fragile. I did this guy in trying to get him under the scope, so I don’t have a better pic. It has been a very wet fall here in northeast GA and I suspect the water is driving them to higher ground. They are driving the wife nuts and need to find out what they are and how to get rid of them.
30 miles NE of Atlanta, GA

Bathroom Fly Larva
Bathroom Fly Larva

Dear Jim,
We believe this is the larva of a Bathroom Fly or Drain Fly which is pictured on BugGuide.  They are also called Moth Flies and are in the subfamily Psychodinae.  The tiny mothlike adults are frequently found in bathrooms, and the larvae live in the drains.

Letter 2 – Bathroom Fly from Romania


Subject: Insect identification
Location: Iasi, Romania
April 5, 2016 1:50 am
please help me identify this insect. It’s been in my bathroom since quite a few years, and lately in my kitchen too. I live in a block of apartments. It’s about everywhere, and doesn’t fly very well or for a long time. It’s small, about 3-4 mm long/wide.
Thank you very much!
Signature: Alex

Bathroom Fly
Bathroom Fly

Dear Alex,
The Bathroom Fly or Drain Fly is a common household pest that breeds in the sludge that accumulates in household plumbing.

Dear Daniel,
thank you very much! Now I can look forward to removing this pest.
I really appreciate your input!
All the best,

Letter 3 – Bathroom Fly from Portugal


Please indicate us another bug site
Fri, Dec 12, 2008 at 3:14 AM
Please indicate us another bug site where we can place this question. We’d like to think we didn’t lose time with this for nothing. Thank you.

Bathroom Fly
Bathroom Fly

Original Letter
Date: 12 June 2008 15:38:25 BST
Tiny Moths
Dear bug-watchers:
We don’t know how vulgar these might be over the world but they are already very familiar to us in (the North of) Portugal. They obviously like humidity in darker places. Lately there was a problem with our WC vent and some very small dark stains (fungus colonies?) appeared on the ceiling & top of the walls. Coincidentally these sort of tiny moths appeared and started to multiply themselves (though I haven’t found any pupas or so) or coming from who-knows-where…
I fixed the problem with the vent but before I expelled the whole bunch (one by one, out the kitchen window) I made these shots of 2 or 3 individuals. Their size is approximately w5mm x h4.5mm.
They’re not buggering at all. In fact, they don’t like to be buggered themselves. Their behavior could be described as very relaxed or lazy. They can fly away like fruit-mosquitos but if they really really have to move then they rather jump away from the threat, which anyway has to be manifested very close.
I only threw them out because I don’t know what kind of bacteriological environment they might start.
Where can we see a little more info on these sort of tiny moths? We need to know if this fellow on our tap was having a funguses snack or taking some sips of our water, in which case it would be fair to share the bill with us.
Dalion & Diana

Bathroom Fly
Bathroom Fly

Dear Dalion and Diana,
While we understand your frustration at not having your letter answered in six months, there is no need to look any further than What’s That Bug? for your answer.  Your original letter arrived while we were in Ohio visiting Mom and planting her tomato plants.  Hundreds of emails arrived in our absence, and we can honestly say that hundreds went unanswered.  Between May and September, What’s That Bug? gets over 100 emails per day and we are a small operation that can only answer possibly a quarter of those letters and some days we can post about 10 letters to our site.
This is a Bathroom Fly, Clogmia albipunctata.  It is a Moth Fly in the family Psychodidae.  The larvae live in the sludge that accumulates in drain pipes.  Now that you know what they are, you should be able to find additional information online.  We like that your background color of your composite matches our website.

Bathroom Fly
Bathroom Fly

Letter 4 – Bathroom Fly in Canada


bug found in the mens washroom at work
July 13, 2010
Hello – a very silly request so I apologize in advance – but there’s a fly in one of our washrooms here at work that i’ve never seen before. Googling does not get me the results I hope for.
Bored at work
Toronto, Canada – 6th floor

Bathroom Fly

Dear Bored at work,
We wondered if perhaps the problem you had identifying this Bathroom Fly (yes that is its name) had anything to do with the semantics of the word “washroom” as opposed to bathroom, so we did a search of “fly” and “washroom”.  On the first page of possibilities was a website with an image of your creature.  Bathroom Flies in the subfamily Psychodinae are also known as Moth Flies, Drain Flies, Sewage Flies or Filth Flies according to BugGuide.

Letter 5 – Bathroom Fly from United Arab Emirates


Subject: Tiny weird moth
Location: Abu Dhabi United Arab Emirates
March 17, 2015 6:50 am
These little moths are all over my house and stick to the walls. They are about a half cm wide and a half cm tall. I just have no idea what they feed on or how to get rid of them. Please let me know! Thanks!
I live in Abu Dhabi… Very hot weather.
Signature: Busjam

Bathroom Fly
Bathroom Fly

Dear Busjam,
This Bathroom Fly or Moth Fly is a common cosmopolitan household pest.  They are generally found in bathrooms as the larvae live in the sludge that accumulates in plumbing pipes.

Letter 6 – Bathroom Fly


Moth like insect
September 2, 2009
I found this insect sitting on my wall. It is about 2-3 mm in length. I took my camera and clicked this snap. I am not able to identify this one. Appreciate if you can help me to find this out.
Sunnyvale, California, USA

Bathroom Fly
Bathroom Fly

Dear Sanjay,
This could well be the most detailed image of a Bathroom Fly, Clogmia albipunctata,  we have ever received.  According to Charles Hogue in Insects of the Los Angeles Basin:  “The Bathroom Fly is often noticed indoors in damp areas – on the walls of bathrooms, showers, lavatories, and washrooms.  The brown worm-like larva develops in the sludgy organic muck that accumulates outdoors in shallow pools and tree holes and, under artificial conditions, in sink traps, drains, and dead-flow areas in the household plumbing.”  Your observation that this is a Moth like insect is right on since the family Psychodidae, is know as the Moth Flies.

Thanks so much Daniel. The information was helpful. I do photography as my hobby and just love macro photography. Will definitely use your website for any bug identification. Your site is of great help.

Letter 7 – Bathroom Fly from New Zealand


small moth
February 27, 2010
i could not find anything on this bug, so i hope you could tell me what it is! it is a moth that i found on one of my walls inside, it is the second one i have seen this month- have not seen before! it is small, about half a centimetre long.
New Zealand, North island.

Bathroom Fly

Hi shayni,
THough it resembles a moth, this Bathroom Fly is really a fly in the subfamily Psychodinae, the Moth Flies.  There are genera in the subfamily that look alike, and BugGuide pictures many species found in North America.  Bathroom Flies or Filter Flies as they are also called are often found indoors in damp bathrooms because they breed in the muck that accumulates in plumbing.

Letter 8 – Bathroom Fly from Australia


What the heck might this be
Location:  Queensland. Au
September 18, 2010 12:11 am
Hi guys,
Thanks for the info on the lacewing nymph. Now to this one. It is only about 3mm body length, has antennae and legs like a moth but appears to only have two wings like a fly. Do you have any idea on what type of thing it may be?
The book is looking good, hope it sells really well.
Signature:  aussietrev

Bathroom Fly

Hi Trevor,
This is a Bathroom Fly or Drain Fly, probably in the genus
Clogmia in the Moth Fly family Psychodinae.  According to BugGuide:  “Adults often found around sewage installations, in public washrooms, and bathrooms in homes, and are attracted to light; larvae live in organic sludge that forms on inner surfaces of drains and sewage pipes; pupae occur on the surface of the organic film that the larvae have been living in.


  • Bugman

    Bugman aka Daniel Marlos has been identifying bugs since 1999. is his passion project and it has helped millions of readers identify the bug that has been bugging them for over two decades. You can reach out to him through our Contact Page.

  • Piyushi Dhir

    Piyushi is a nature lover, blogger and traveler at heart. She lives in beautiful Canada with her family. Piyushi is an animal lover and loves to write about all creatures.

16 thoughts on “Life Cycle of Drain Flies: Understanding & Managing the Pesky Intruders”

  1. Hi bug man , my name is Mary I read a LOT of your stuff and I hope you can help me I don’t know what I came in contact with the only thing I seen was drain larva and I’m so confused about what’s going on with me and this big problem with drain fly it got so bad me and my husband after 35 years are getting a divorce . My oldest son says it’s all in my head and my doctor says I’m hausanating I know what I see it started with my nose when I would blow it I notice it was different I’m sorry it’s gross but I’m despert I can’t even see my grand children . Course I don’t know if I’m contagious tut not like a worm you would see out side, this is scary the E room doc gave me the medication abenzol, 3 prescription @ 12 pills and I’m still infected Iits getting worse do you have any idea what it is .im so aggravate and fear it’s going to take my life.every thing changed.if it is drain fly related what can I do to get rid of it course the larva I’m seeing in the drains in the sink it raps it self around the drain looks like it has stripes on top when I blow my nose it comes out clear but I use a nasal mist and that gives it color and OH my it’s the ugliest thing I ever seen in my l life it connects point in the front and one end has like hair can you help me please I read there’s 3 stages of this pest I think I’m at the 2nd stage the larva I’m seeing in the toilet is a white cloud. I can’t wait to hear back from you thank you. Thank you

  2. I originally came to this website to identify the bathroom fly, but the info was already there. What i want to know is do they lay eggs on piping hot food because several times I’ve had to fight one away from a plate of very hot food. They woud be very close or even on the food even though it was very hot. So i was wondering what attracted them so much to extremely hot food. Do they want the food or are the trying to lay eggs.

  3. Bathroom fly is resistance to insecticide. It is also carrier for the disease called klebseiella. Only a combination of antibiotic klassid and xylid can cure it by taking over a period of over two to three months. As bad ad tuberculosis. It is sometimes called second TB. Pstch all holes in the bathroom and keep it clean.


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