Farmer and Circle Flies

An old farmer was hauling a load of manure when he was stopped by a state trooper. "You were speeding," the cop said. "I'm going to have to give you a ticket."
"Yep," the farmer said as he watched the trooper shoo away several flies.
"These flies are terrible," the trooper complained.
"Yep," the farmer said. "Those are circle flies."
"What's a circle fly?"
"Them flies that circle a horse's ass," answered the farmer. "Them are circle flies."
"You wouldn't be calling me a horse's ass, would you?" The trooper angrily asked.
"Nope, I didn't," the farmer replied. "But you just can't fool them flies.

Farmer and Circle Flies - An Old Farmer gets the best of a sheriff.