Home filled with flies--are they getting in chimney?

dreambuilderFebruary 22, 2014

Anytime the weather warms up (we live in super cold climate) we have a huge surge of flies coming into our house--to the point they are covering our windows--hundreds of them. I have had to start vacuuming them up several times of day. I have checked windows--none are open. The only place I can think they are coming from is our fireplace cap on the roof. Is that possible? I know it is rusty so I'm not sure if that would be reasonable? The flue is open but they seem to get in even when I close it. I have seen flies crawling around the fireplace opening. I was quoted $400 to replace it. Could I do it myself? Doesn't seem that complicated? Has anyone had flies come in like this before?

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Chances are the flies are not coming into the house through the chimney or any other opening to the outdoors. Instead, they are hatching from eggs deposited in the house. They began as eggs, have gone through the larval stage and are now emerging as adults. Warmth speeds up the process which would account for their appearance after a warm spell. The larva need a food source which can be a great many things. (Could there be a dead bird in the chimney?) Your county extension service or state agency that deals with insects should be able to identify the partiular species of fly which can help in tracking down where they are coming from.

    Bookmark   February 23, 2014 at 6:15AM
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You probably have cluster flies. We had them in our old farmhouse in NH. Try googling them. We treated the attic and upstairs--maybe some sort of bomb while we were away. It helped for a while but then they gradually returned over the years.

    Bookmark   February 23, 2014 at 11:35AM
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We do have a second floor but none of them are on the second floor--they are all on the main floor? Some act sluggish but some of them are very speedy? I would think if we had a dead bird we would have smelled it? I had the chimney inspected by an idiot--he didn't go on the roof, and I'm sure just shined a flash light up there so anything is possible--although it does have a cap so I don't know what kind of bird could get in there--but if it is a dead animal they eventually decompose so why would they keep coming back like this? Once you have cluster flies do you ever get rid of them? It is really disgusting sometimes they just fall from the ceiling onto kitchen counters, floors, etc. Very gross.

    Bookmark   February 23, 2014 at 11:47AM
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Cluster flies deposit their eggs in the soil, use earthworms as a food source for the larva and emerge as adults in the fall, not mid-winter, so it's very unlikely this is what you have. Other fly species commonly deposit their eggs in animal corpses but can utilize just about any kind of decaying organic matter which serves as a food source for the larva when they emerge. Flies deposit eggs several times, not all at once, so you are probably dealing with multiple hatches. That's why they seem to disappear and then come back. Eventually they all will have emerged, lived out their short lifespans and died. What you don't want to happen is more eggs deposited in your house while they're alive.That's why identifying the species is important. So is eliminating any possible decaying organic matter, but if it's in an inaccessible place like a wall cavity it's nearly impossible.

    Bookmark   February 24, 2014 at 6:28AM
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we had the same thing and indeed there was a dead animal. It was in the furnace flue - believe it or not- not in the fireplace flue (1 chimney w/ 2 flues). The chimney cleaner was surprised (he almost didn't check) that the squirrel managed to die down that flue. We found it when we opened the little metal door into the chimney that was in the furnace room in the basement.

    Bookmark   March 23, 2014 at 12:28AM
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