Black Fly Infestation in Small Basement Bathroom

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Old 06-25-20, 01:44 PM
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Black Fly Infestation in Small Basement Bathroom

I went into my basement bathroom today and found the toilet covered with about twenty of these big black flies. There were also a few scattered around on the walls and floor. It is a small bathroom with just a sink and toilet and I have never had a bug issue there before. The flies were very easy to smash as they seemed oblivious to my presence. This is my man cave bathroom and I have not seen any flies buzzing around the basement. There is an attached laundry with a cat litter box (which I clean daily) but I did not find any flies in the laundry. There is a floor drain nearby, but I took the plastic cover off of it and there were no bugs there. There also do not seem to be any flies in the cabinet under the sink. This whole situation kind of freaked me out as I have lived here for 20 years and have never seen this in the past, nor really experienced any insect problems. The flies looked just like the ones shown in the following post:

https://www.doityourself.com/forum/i...-bathroom.html

Any ideas?
 
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Old 06-25-20, 04:03 PM
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The fly pictured in the post that you linked to is the common "house fly" sometimes confused with the "stable fly" or "false stable fly". Assuming the housefly ID is correct, they do, according to the article, breed in sewage and animal waste among other things. Wherever fly populations are the densest is generally close to the source. I wonder if the toilet may be coming loose from the floor or is the wax seal shrinking? If you see new arrivals, consider taping the gap where toilet meets the floor. If that's where they are emerging from, then possibly you'll catch some on the tape.

What is underneath the house/bathroom such as basement, crawl space, slab?

house fly - Musca domestica Linnaeus
 
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Old 06-25-20, 07:02 PM
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This is a basement bathroom, so I assume under the tile there is the cement foundation. I will try the tape idea, but I've got to say, these flies are bigger than the typical Houseflies that I normally see and like I said, they are very docile.
 
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Old 06-26-20, 06:20 AM
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If the problem persists we will need our own picture of the flies that you are seeing. The fly in the post that you linked to is the common house fly. I assumed that you were offering this as representative of what you are seeing in your bathroom. If possible, show us pics of top and bottom of the flies in your bathroom. Top pics especially. Houseflies have longitudinal stripes on the back, red eyes, and note how the wings are at rest compared to other flies. Some quick features to compare with yours.

Taking specimens to the local county agricultural extension agent is a good thing to do as they will offer objective info; won't try to sell you something.

Maybe cover the floor drain temporarily with tape facing down towards the drain, too. In the post you linked to, I saw advice suggesting that the bathroom vent duct, if there is one, should be inspected for birds, rodents, debris, etc. and to make sure that it is closing.
 

Last edited by PAbugman; 06-26-20 at 06:38 AM. Reason: more info
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Old 06-26-20, 01:49 PM
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The flies seem to have abandoned the bathroom and are now buzzing around in the main room and the laundry. I inspected the toilet and it seems to be anchored to the floor in the proper manner. I took the plastic lid off the floor drain again. It is wet in there as that's where my dehumidifier drains, but no sign of insects or flies. I will try to get a picture of the culprits, but I don't have a smart phone so it will be a more involved process to post a pic. I have probably killed a dozen of these flies in the past hour, mostly hanging around my ceiling light. They are much easier to kill than my previous experience with house flies. They basically just sit there waiting for you to swat them and even if I miss, they come right back to give me another shot.
 
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Old 06-26-20, 04:05 PM
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Cluster flies are sluggish and slow but this isn't the right time of year for them, though sometimes insects don't obey all the rules. Cluster flies resemble house flies, too. Read about them and see what you think.
 
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Old 06-27-20, 01:47 PM
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I've looked at a few of these flies under a lit magnifying glass and it's obvious they are not all the same. Some of them do have red eyes and black and yellow backs. Some have black eyes and shiny blue bodies, what we used to call bottle flies. They are pretty much restricted to the laundry now, probably because I keep a light on constantly back there.. Haven't seen any in the bathroom since that first day. I covered the floor drain with a towel and plan on spraying the drain daily. I appreciate all the information and help you guys have given me. I would say that the problem is slowly getting better, but perhaps I am in for a nasty surprise down the road.
 
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Old 06-28-20, 08:23 AM
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The presence of bottle flies could indicate that a rodent, bird, etc died in a wall or ceiling somewhere and is decomposing. That could be why you haven't noticed this before now. Just a thought.

Check all exhaust vent hoses, flappers etc as best you can.
 
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Old 06-28-20, 05:52 PM
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After swatting at a couple of flies every time I went back to the laundry room last night where the refrigerator is, I woke today to find them absent. Don't know if this means the issue is closed or not. I guess time will tell. In any event, I appreciate all the knowledge and advice presented here the past couple of days. If they return, I might as well.
 
 

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