A cowboy from Texas was pulled over by an Arizona DPS Trooper for
speeding. The trooper started to lecture the cowboy about his speeding,and in general began to throw his weight around to try to make the cowboy 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 cowboy said, "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 no circle flies."

Well, sir," the cowboy replied, "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 said, "Oh," and went back to writing the ticket.

But, a moment later he stopped and said, "Are you calling me a
horse's ass?"

"No, sir," the cowboy replied, "I have too much respect for law
enforcement to call y'all a horse's ass."

"That's a good thing," the trooper said and went back to writing the
ticket.

After a long pause, the cowboy, in his best Texas drawl said, "Hard to fool them flies though.