How can you distinguish between a male fly and a female fly?

Male and female fruit flies can be distinguished from each other in three ways: 1) Only males have a sex comb, a fringe of black bristles on the forelegs. 2) The tip of the abdomen is elongate and somewhat pointed in females and more rounded in males. 3) The abdomen of the female has seven segments, whereas that of the male has only five segments.