My horses have been plagued by massive flies. They (the flies) are nearly an inch and a half long, usually light grey with transparent wings. The eyes are black. I see them on my horses' necks and shoulders, never the face, and around the inside of their hind legs and sheaths. They definitely suck blood, and leave a soft welt where they bite that disappears after a few hours. I have tried every fly product I can afford (Farnam's Bronco seems to get rid of everything but these suckers). One horse is foundation bred quarter horse, and the other is a mutt, but basically quarter horse as well, if that matters. The giant flies are worse on the mixed breed, but he has a lot of chrome (all four legs to the knees and a blaze). Please, help me identify these bugs and find something to get rid of them! I will try to get a picture of the beasties up soon.
Try a fly sheet perhaps? Or those fly strips that you hang on the horses legs?
I don't know what they are.
We have deer flies that hurt like heck when they bite. We also get huge horse flies in the middle of summer, they can be about two inches long. The best way to kill them is to smack them with your hand. Gross, but effective!!
Does sound like horseflies but without a photo it's hard to say. I have never found a catch-all solution for horseflies, but I would search the 'net for you if my internet wasn't so slow tonight... Maybe try to encourage some birds to hang out by the barn and paddock. Put up some feeders and a birdbath.
You don't have horse flies in Montana Spastic? That's odd. We have them all over down here combined with deer flies. Both are just vicious and are willing to attack people and animals. They are most prevalent in areas with trees along a creek or the bottom of a dry canyon.