Species-specific differences in the behavior of male tsetse fly genitalia hidden in the female during copulation

One possible explanation is that male genitalia are under sexual selection to function as ‘internal courtship devices’. Males of closely related species may provide divergent stimulation using different genital morphologies and behaviors.

Testing this hypothesis has been difficult, however, because the presumed genital courtship behavior is often hidden from view inside the female, and because studies of how the male’s genitalia interact with those of the female are nearly always limited to a single species in a given group, thus restricting opportunities for comparison of closely related species. We present new morphological and behavioral data for portions of the male genitalia that are hidden in the female during copulation in five species in the tsetse fly genus Glossina using data from dissections of pairs frozen in copula, artificially stimulated males, and from copulating pairs viewed with a new X-ray technique that allows events inside the female to be recorded in real time.