During a traffic stop a police officer is swatting at a fly that is circling around his head, and blurts out what kind of damn fly is that anyhow. The traffic offender replies, thats a circle fly. The officer replies that hes never heard of a circle fly. The offender replies circle flies are usually found circling around a horses ass. Enraged, the police officer says, are you calling me a horses ass?, to which the traffic offender replied, no sir, but you cant fool a circle fly.