Traditionally, morphological differences in male genitalia have been used to differentiate similar species of Lepidoptera. While other characters may be examined, it is often assumed that genital morphology is the unique characteristic that "defines" a species. The significance of this assumption is based, many times unknowingly, on the lock-and-key hypothesis, which states that male and female genital compatibility serves to reproductively isolate different species. This concept was tested by quantifying the shape of the male valva in the genus Hystrichophora, and analyzing this character in individual populations using principal components analysis. Results show extreme intraspecific variation in genital morphology, supporting Eberhard’s proposal of sexual selection by female choice but rejecting the traditional lock-and-key hypothesis.