The male and female housefly

There lived a husband and a wife.One afternoon,the man came from work and saw his wife in the kitchen stragling with house
flies.He asked,dear what is the matter?.
She answered,am killing house flies.
He was suprised and repeated,HOUSE FLIES????
Yes she answered,I got two males and three females.
Then he aske,how did you know?
She answered,the males were on the beer bottle and the females were on the telephon