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.