Practice immobilizing and sexing these flies. Examine these flies and note the characteristics of their eyes, wings, bristles, and antennae. To make handling easier, immobilize the flies with fly-nap, or by twirling the vial in ice for several minutes. Place the immobilized flies on a piece of filter paper inside a petri dish. Place this under a dissecting microscope to view the flies.
Males are usually smaller than females.
Males have dark, blunt abdomens, and females have lighter, pointed abdomens. Only males have sex combs. which are groups of black bristles on the upper most joint of the forelegs. Obtain a vial containing pairs of experimental flies. Record the cross number of the vial. This number will serve as a record as to which cross you obtained.