In the last few days I have noticed a lot of large striped black house flies in my house. It appears that they are coming from somewhere in my house but I cannot find the source. They are different looking than the normal house fly, the body is longer and they are actually a little slower. I am wondering if anyone knows what kind of fly this is. I live in SE Wisconsin.

Do they look like these?

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We live in western North Carolina and are experiencing the same problem. Not sure where they are coming from or how to get rid of them. We kill 10 to 20 each night which seems like it is all that is in the house and by the next day there are just as many in the house again. Very frustrating, can any one give us some answers?

Zafero, yours sound different than eileen's

I suspect what you have are cluster flies.
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Check your attic, they may have decided to overwinter there. If you find a lot (dozens if not hundreds), set off a fogger and check in a couple of days.