Flies
A woman walked into the kitchen to find her husband stalking around with a fly swatter.
"What are you doing?" she asked.
"Hunting Flies" he responded.
"Oh. Killing any?" she asked.
"Yes, 3 males and 2 females" he replied.
Intrigued, she asked, "How can you tell?"
He responded, "3 were on a beer can, 2 were on the phone."
(thanks to Art Drysdale)