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Pest Control/Flies and beetles coming from bathtub drain and possibly from walls as well?



The bathroom is situated on an outside wall of the house, so the shower wall is also the exterior wall to the house. On that wall is an unopenable window. Right outside the wall, we did have a tree cut down and the stump ground down and there is a good amount of mulch in the area from the stump being ground. We plan to clean everything up and do some landscaping but just have not yet. I don't know if that could be a possible source but I'm mentioning it just in case.

About a week and a half ago, I started noticing a couple small flies in my bathroom, and only my bathroom. I killed them and didn't think much of it. After a couple more days, more flies starting coming out and additionally, some type of hard carapace 'beetle' starting appearing as well.

I took apart the bathtub hardware, took off the safety drain plate and put tape and other see thru but impenetrable films to see if they were coming from the drain and in fact they were.
I started treating the drain with boiling water, drano, baking soda/vinegar, pesticides. Nothing has helped. The drain is very clean from what I can see, but I have not tried a snake or any type of pipe scum cleaner that is recommended for drain flies. However I know based on photos that these are not the moth type drain flies. I had my pest guy out here and he could not tell what they were either since he had never seen anything like it. I'm awaiting him to reach out to his entomologist as well.

They still are in the one bathroom and only that bathroom. I have not noticed them coming out of the sink drain or the adjacent bathroom either. I have seen a couple of both the flies and beetles flying in the adjacent bedroom but I believe they just happen to get out of the bathroom. Also of note, I do find some are dead already by the time I see them.

Black 'flies' - 1 to 2 mm in length, black, flying, attracted to the window in the shower stall.
Black 'beetles' - 3 to 4 mm in lenth, black, hard carapace, attracted as well to the window but found crawling over the floors and well as brief spurts of flying as well. I need to wad them up in a piece of tissue and crush them to kill them.

In my research, the only thing I can compare the flies to are fungus gnats, but I feel these flies are too 'fat' and not mosquito like compared to the gnats.
For the beetles, I have not found anything.
I can provide more photos upon request if allowed.

I am in Miami, Florida, USA.


I think these are both phorid flies ( and I can't see them clearly enough to be certain but since there are no beetles that typically emerge from drains (and phorid flies sometimes do) I'll stick with that guess. Phorid flies sometimes enter drain systems through a break in the line so check the line if possible. The fact that normal drain cleaning has not worked indicates that perhaps the source is further down the system. Cleaning and repairing a breaks in the drain system is the best approach to phorid fly control.

Jack DeAngelis

Pest Control

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Jack DeAngelis


I can answer questions about the control of pest insects, spiders, mites and related arthropods. These household pests include termites, carpenter ants, powderpost beetles, nuisance ants, bed bugs, cockroaches, fleas, wasps, and many others. I can also answer questions about using pesticides and other pest control tools such as baits and traps.


I am a retired university extension entomologist. I've taught and conducted research in urban and agricultural entomology. I've published over 70 extension publications, 20 research publications and several books about insects.

Ph.D. in Entomology

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