Hard To Fool Them Flies

A cowboy got pulled over by a state trooper for speeding.   The trooper
started to lecture the cowboy about his speed, and in general began to
throw his weight around to try to make the cowboy uncomfortable.
Finally, the trooper got around to writing out the ticket, and as he
was doing that he kept swatting at some flies that were buzzing around
his head. 

The cowboy asked, "Having some problems with them circle flies there,
are ya'?" 

The trooper stopped writing the ticket and said, "Well yeah, if that's
what they are. I never heard of circle flies." 

So the cowboy says, "Well, circle flies are common on farms and ranches.
They're called circle flies because they're almost always found circling
around the back end of a horse." 

The trooper merely says, "Oh," and goes back to writing the ticket.
After a couple of minutes he stops and says, "Hey... wait a minute,  are
you trying to call me a horse's ass?" 

The cowboy replies, "Oh no, Officer. I have too much respect for law
enforcement and police officers to even think about calling you a
horse's ass." 

The trooper says, "Well, that's a good thing," and goes back to writing
the ticket. 

After a long pause, the cowboy says, "Hard to fool them flies though."