Where could a bunch of flies in my house be coming from?

Since you mentioned cats, perhaps there is a dead mouse cleverly hidden or even entombed inside a wall.

The professional cleaning probably got rid of the spiders that have been eating the flies.

Are they small flies or big ones? The big ones mean something dead is around.

The flies may be hatching inside your house, which is why you have more today.

@YARNLADY: She’s been cleaning here about 3 years, so whatever she’s been doing has been done for years before this.

@zenvelo: They’re green and they’re reasonably big. They’re also not the fastest, as I was able to kill them last night fairly easily.

This makes me want to check around for something dead. Gross thought but flies are not exactly a pleasant thought, either.

OOHH @gailcalled been there, had that happen.
@jca is it possible that they are “cluster flies”? Here is the link for Cluster Fly

I just looked at the link for Cluster Fly and looked carefully at the flies that are on the lamp by my bed, and the ones in my house are green and the ones in the cluster fly picture are not, so I don’t think it’s the same fly.

@Tropical_Willie: We have cluster flies seasonally; they enter the house in the late fall and leave by mid-April. So this is the wrong time of year.

I leave doors open now in order for his royal highfalutin’ catness to have instant access to the house and grounds. By nightfall, when I bring him in and shut everything, I have to swat many common house flies. Green flies might be deer flies. Houseflies have a green glitter under the right light.

No picture, just guessing. The cluste fly will move in dut=ring the summer.

I don’t smell anything weird in the room. I just gave a glance under the bed and don’t see anything.

It was a mild winter so there was less winter kill of insects in our area. Therefore we have more flies, more ticks, more fleas and generally more creepy crawlies than usual. Could that be contributing to your problem?

@WestRiverrat: It could, but this has been very noticeable in just the last two to three days, so that’s weird.

If one of the traps in your sewer line has dried out, they could get into the house that way. Especially if your sewer vent is not screened.

Dead rat in the attic

From here

My thought is a ditto of @WestRiverrat. If you have any floor drains (laundry area/basement) pour water down them.

Check your window screens for holes.

I forgot about a potato in a drawer once. It ended up smelling bad too.

Are any of your windows open and unscreened? Is there something outside the house but close enough to draw flies towards windows?

Check the drain pan under the refrigerator. If it collects any accumulation of water from the auto-defrost process, then it’s a convenient watering place for mice and other small critters, and if they happen to die there (maybe after being wounded from a cat), then it’s not a place you’d often check.

They solnd like green bottle flies. If, they are then you likely have something dead in the wall, basement block, etc.
The good news is they are easy to control. Hang a strip of fly paper near a light for a couple of days. A typical brood is only about 20–30 flies at a time so you can get the whole colony in 3–4 days and feel confident you got ‘em.
I know fly paper is disgusting but it really works. Just do it.

I used to live across from some people with a couple of horses; in the morning the sun was on the paddock, and over the course of the day, the sun moved over to our dooryard. By late afternoon, the paddock was shaded and our driveway area by the door was sunny… the flies followed the sun and ended up all around our door. Maybe you have a similar sort of thing going on? Where whatever they are attracted to isn’t right next to you, but they end up near your house, and there is somewhere they can get in… just a thought. Flypaper is a good idea, but whatever you do, don’t put it somewhere you might forget about it and walk into it!!:-P

Tonight I am going to move the refrigerator away from the wall and look under it, and move the couch away from the wall and look under that. I see each room (during the day) has about 2 or 3 flies in it, but at night, they congregate in my room, where the lights are on and the whole rest of the house is dark.

Last night my daughter was drinking a glass of water and it had a fly in it, and that was just gross. I tore the bed away from the wall to see if there was anything under it. I am aware that there could be a little mouse or something that’s really small and dead behind a piece of furniture, but I figured I’d start with the couch and the refrigerator.