Sexing Flies

Joan found her husband George Indulging in a strange caper Stalking about the kitchen With a rolled up newspaper "What on earth are you doing?" She asked with annoyance. "I’m doing battle with flies" Was his proud response "Have you killed any yet?" She asked, walking to the door "Three male and two female Is the current score” "How can you sex a fly?" Asked a now interested Joan "I killed three on a beer can; The other two were on the phone"