Several hypotheses attempt to explain why male genitalia typically diverge rapidly over evolutionary time. Predictions of the lock and key and the sexually antagonistic coevolution hypotheses were tested by studying the functional morphology of several male genitalic traits by freezing copulating pairs of four species of Drosophila: saltans, willistoni, melanogaster, and malerkotliana. Contrary to the predictions of the hypotheses, there were no species-specific differences in female morphology that corresponded to interspecific differences in the morphology of the male surstylus (which pressed and perhaps spread the distal tip of the oviscape), the epandrium (which grasped the external surface of the extended oviscape), and the aedeagus and paraphyses (which, in willistoni, clamped the oviscape). Antagonistic coevolution could possibly explain the diverse male genitalic morphology if female resistance behavior rather than morphology has coevolved with male morphology, but there are reasons doubt this explanation.