Hunting 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," responded her husband.
"Oh. Killing any?" she asked.
"Yep, three males and two females," he replied.
Intrigued, she asked, "How can you tell?"
"Three were on a beer can, and two were on the phone," he replied.