Circle Flies (joke)

The trooper started to lecture the Okie about his speeding and, in general, began to throw his weight around to try to make the Okie feel uncomfortable.
Finally, the trooper got around to writing out the ticket. As he was doing that, he kept swatting at some flies that were buzzing around his head.
The Okie says, "Y'all havin' some problem with circle flies?"
The trooper stopped writing the ticket and said, "Well yeah, if that's what they're called. But, I never heard of circle flies."
"Well, sir," the Okie replies, "Circle flies hang around ranches. They're called circle flies because they're almost always found circling around the back end of a horse."
The trooper says, "Oh," and goes back to writing the ticket. But, a moment later he stops and says, "Are you callin' me a horse's ass?"
"No, sir," the Okie replies. "I have too much respect for law enforcement to call y'all a horse's ass."
"That's a good thing," the trooper says and goes back to writing the ticket.
After a long pause, the Okie, in his best southern drawl, says, "Hard to fool them flies though."