How to tell the sex of a fly 
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. 
"Yep, 3 males, 2 Females," he replied. 
Intrigued, she asked. 
"How can you tell them apart?" 
He responded, 
"3 were on a beer can, 
2 were on the phone.