lisah, it has to do with breeding conditions.

Try www.edis.ifas.ufl.edu/search

and search for biting flies.

Fly larva need moist, decaying, organic matter to hatch and grow on so somewhere around there must be a lot more of that than you had before. Eliminate that breeding ground, or have you local unit of government do that,and you will have fewer flies.

Thank you both for the info! My husband recently dethatched the lawn, which resulted in about a dozen trash bags of thatch. I'm willing to bet that's where they're coming from. Of course, convincing him is a different matter...

Thanks,
Lisa

Flies have swarmed my flower patch in the last week and are covering my sunflower plants (not yet blooming) and other flowers that have been there for many months, the wall, the steps, everything! I have searched for dead animals, garbage anything that may have attracted them and can find nothing. The sunflower seedlings are about 7 weeks old, but I don't think that is the draw? Anybody got any ideas of why and how to get rid of them without harming my bees, butterflies, squirrels, birds, cats and dogs? There are big spiders now, too, catching some, but not enough.

Where the flies are breeding can be quite some distance away, a mile or more. You can put up those strips of flypaper, encourage more predatory insects, and birds, to hang around and over time the flies will diminish.

Biting flies need quite a bit of moisture to breed - swampy or mucky areas, or even streams. I don't think they are breeding in your bags of thatch.