The interaction of male and female genitalic morphology is an essential component of post-copulatory processes, and has the potential to provide key insights into the evolution of diverse genitalia in both sexes. In this study, discrete characters of male and female genitalia were mapped onto a phylogeny of the Phyllophaga s. str. using parsimony and maximum likelihood ancestral reconstruction methods in Mesquite. Correlated evolution of male and female characters was then tested using parsimony and likelihood methods in the programs MacClade and Discrete. The characters chosen for analysis include the hook-like parameres at the distal end of the male genitalia, and the sclerotized pubic process of the female genitalia extending from the two genital plates. These two structures have a direct interaction during copulation; the parameres of the male genitalia are inserted into the female and hook into the female pygidial hemisternite, while the female pubic process is inserted between and hooks underneath the parameres of the male. Correlative analyses provide a means to test whether selection is acting on male and female structures to produce similar patterns of divergence, or whether each is evolving along their own trajectory. If female structures are evolving independently of male genitalia, one could assume divergence due to drift or natural selection. However, if female genitalia have coevolved with male genitalia, divergence in female genital structure could potentially influence the differential fitness of her mates, thus becoming a candidate for post-copulatory sexual selection.