What measures have you taken in the past? Do you live near a breeding ground (pond, creek, lake)? Is there a large population of animals (including humans) that support these awful flies?

We don't live near water and there are no animals anywhere near. This just seems to be a problem almost every year around this time. We did just recently have rain after a month of drought, I don't know if this made a difference, but we do have a lot more bugs in general after the moisture.

2 summers ago I had tons of flies bothering me on new deck I built behind my house.

I tried sprays...no luck, I tried those sticky strips...no luck. I tied an electic bug zapper...no luck. Finally I just took a fly swatter with me every time I was on the deck.

The next spring I bought a farm/barn fly trap at a local farm/ranch store. It's a plastic bag with a vile of really smelly goo in it. You break the vile add water and hang up the trap. It was about $4. I hung mine near the new deck on my humming bird feeder pole. It was about 4 feet off the ground. I've also seen traps like this at Wal*Mart this past year.

The trap worked! No flies this year or late last year.

It was full of flies in one weekend and I must have caught 1 to 2000 of them in the 2.5 months I had it up. The more flies you catch the stinkier it gets...which attachs more flies. They can fly into the trap but the design is such that once in they can't find the way out. And they just drown in the brown liquid. When you are done with it you just trash can it.

No toxic chemicals nor sprays.

You have to watch out for the wind driven smell as it's like a "ripe diaper". I moved mine a time or to...when the wind was blowing the wrong way... :-)

Pete in Iowa

Eat lots of garlic!

Attract birds that eat them...

You have those flies because somewhere nearby is a breeding ground for them. The Horse Fly, or Stable Fly, does need blood from some mammal but the larva from which these adults come need a moist environment to grow in and that can be a garbage pile, animal manures, compost piles, etc.
There are traps you can use to help control the adult flies, but the best solution is to find where the larva are and eliminate that.

Here is a link that might be useful: About Flies

I think you are confusing the horsefly with the stablefly, kimmsr. Though common names can be confusing, the huge fly most of us know as the horsefly isn't a manure or garbage fly....stable flies are.

I try to remember that horseflies are basically pollinators. The female only goes hunting some blood to process eggs.

rhizo, according to the entomolgists I have talked with the Horse Fly and Stable fly are the same critter. Of course I understand these learned people could be wrong.

Well, considering the fact that the two insects look completely different from each other, are found in totally different environments, and behave differently from each other....I'd say that there is some confusion going on with these talks with your entomologists. ;-)

The most obvious difference is their comparative sizes. A horsefly can be as large as an inch in length. I have personally seen them that big. Knowing that something that big wants to take a bite out of you is extremely intimidating, to say the least. Stable flies are often mistaken for houseflies.