From the ArcaMax Publishing, Jokes Newsletter:
http://www.arcamax.com/news/jokes/s-15162-857737
After pulling a farmer over for speeding, a state trooper started to
lecture him about his speed, pompously implying that the farmer didn't
know any better and trying to make him feel as uncomfortable as
possible.
He finally started writing out the ticket, but had to keep swatting at
some flies buzzing around his head.
The farmer said, "Having some problems with circle flies there are
ya?"
The trooper paused to take another swat and said, "Well, yes, if
that's what they are. I've never heard of circle flies."
The farmer was pleased to enlighten the cop. "Circle flies are common
on farms. They're called circle flies because you almost always find
them circling the back end of a horse."
The trooper continues writing for a moment, then says, "Hey, are you
trying to call me a horse's behind?"
"Oh no, officer." The farmer replies. "I have too much respect for law
enforcement and police officers for that."
"That's a good thing," the officer says rudely, then goes back to
writing the ticket.
After a long pause, the farmer added, "Hard to fool them flies,
though."