The bot flies and warble flies are an impressive and actually seldom seen group. As adults anyway. Family is Oestridae and there are only about 40 species in North America. I have only seen two free-flying adults. Though, granted, I have never owned large animals. Perhaps keepers of horses and cows and sheep see the adults more often during their short flight time. These adults do not feed so they only live as long as they can on the fat stores they come with.

This one took up a post on this large (and bright white) patch of heron poop on a creek in Arkansas. Seemed to be waiting for something. I cannot tell the sex on these things. There are only six genera in NA. They are Cuterebra (26 species) which parasitize the flesh of rodents and rabbits. Gasterophilus (4 species) which parasitize horses. Hypoderma (3 species) which parasitizes cattle in two and in one Caribou. Oestrus (1 species) which prefers the noses of sheep and was imported from Europe. Cephenemyia (6 species) which choose their particular cervid (deer, elk, moose). Suioestrus (1 species) which likes a nice pig. Here is the short key from the Nearctic Diptera catalog.

By the wing veins this seemed to be a Cephenemyia but I await further information. Eric Eaton says this appears to be a Cuterebra species.