(a) Testing equal amounts of each attractant

At the end of the experimental work, a test was run on the 200 female flies that would have been selected for the fifth generation. When they were fully developed and ready to lay eggs, the flies were given the choice of equal amounts of each attractant to determine whether or not they chose the correct attractant for their strain in a higher percentage than the attractant of the opposite strain. Each strain was given three egg-laying phials of each attractant since it was felt that this would reduce the chances that an accidental heavy laying in one phial would distort the results (this distortion effect is dealt with in the discussion). The experiment was repeated on four successive days.