If it’s houseflies, they are attracted to decaying organic matter. As an above poster mentioned, sometimes that’s scum in your drains, not just garbage or something dead.

Cluster flies come in through cracks. The more air-tight your home, the better. You can also hire an exterminator to treat your house’s exterior, but you need to time the treatments for right before the season when the flies tend to enter.

We have a mouse trap in the attic. When I see flies, I know the trap caught a mouse.

Google cluster flies. I get them time to time thousands of them.

Anonymous wrote:Try running water in all your sinks and showers. If you have a sink or shower you don’t use for a long time, water can evaporate out of the “trap” and allow flies in. Good luck.

Thanks I’ll check. Any idea why they are so heavy in backyard? Is there some plants that attract them? We live in suburban tract housing.

Try running water in all your sinks and showers. If you have a sink or shower you don’t use for a long time, water can evaporate out of the “trap” and allow flies in. Good luck.

We bought a house in Belle Haven section of Menlo Park.

We have been overrun with houseflies since we moved in a year ago.

I assume if something died in walls it would have disintegrated by now, so don’t know why they keep coming.

We have traps outside but still so many flies in the house.

Are we on like a swamp or something?