Male and Female
A woman returned home from a shopping trip to find her husband hurtling around the house like a madman with a rolled up newspaper. "What on earth are you doing?" she asked.
"Killing flies," replied her husband. "I've got four so far, two males and two females."
"How can you tell male flies from female flies?" asked the wife.
"Easy," replied her husband. "The two males were on a beer can and the two females were on the phone."