A woman walks into the living room where her husband is stalking around with a fly swatter.
"What are you doing?", she asks.
"I'm channeling my inner hunter and hunting flies.", he says.
"Hunting flies, huh. How many have you killed, oh great hunter of flies?", she mocks.
"I've killed 5 actually. 3 males and 2 females.", he responds.
Taken aback that her husband can tell the difference between male and female flies she asks, "How can you tell them apart?"
"Easy," he replies, "3 were on a beer can and 2 were on the phone."