Circle Flies

After pulling me over for speeding, a state trooper started to lecture me about my speed, pompously implying that I didn't know any better and trying to make me feel uncomfortable as possible.
He finally started writing out the ticket, but had to keep swatting at some flies buzzing around his head.
I 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."
I 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." i replied. "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, I added, "Hard to fool them flies, though."