Additional Tests

(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.

(b) Eggs as attractants

This test was performed in an attempt to assess the possibility that freshly laid eggs might act as ovipositional attractants. Sample populations of 200 females flies were offered a choice of two egg laying phials, one having the egg laying medium scattered with freshly laid eggs, the other being untreated egg laying medium. Numbers of eggs used as "attractant" were counted before use in order that they would not weight the results of the experiment.

(c) Strength of chemical vs egg attractants

This test was conducted as a corollary to (b). After Generation 4, flies from the amyl alcohol selected strain were presented with a choice of two egg laying phials, one containing egg laying medium and amyl alcohol, the other egg laying medium and eggs. Similarly the ammonium carbonate selected flies were presented with two choices, either ammonium carbonate on egg laying medium or egg laying medium and eggs.

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