Neural control of homosexual courtship in Drosophila melanogaster

Immature D. melanogaster males, like virgin females, often elicit vigorous courtship from mature males. Since males perform the same behaviors in response to attractive males and females, the question arises as to whether the foci--cells in the courting male's nervous system that must be haplo-X for the fly to perform a behavior--are the same for homosexual and heterosexual courtship. To answer this question, we analyzed the behaviors that normal males perform in response to sexually attractive flies. From these data, we calculated the probabilities that a fly with haplo-X tissue in a focus for homosexual and heterosexual courtship would perform the behavior in response to one or both of the two sex objects with which it was tested. Next, we observed the courtship behaviors that gynandromorphs (sex mosaics) performed in response to attractive males and females. Since the numbers of mosaics that performed a behavior in response to one or both of the sex objects with which they were tested were not significantly different from the predicted values, we conclude that the foci for performance of homosexual and heterosexual courtship are almost certainly identical.