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," he responded. 

"Oh!, Killed any?" she asked. 

"Yep, 3 males, 2 Females," he replied. 

Intrigued, she asked. "How can you tell?" 

He responded, "3 were on a beer can, 2 were on the phone."