Spilopsyllus inaequalis inaequalis and Spilopsyllus inaequalis interrupta are common ectoparasites of species of Leporidae. Kohls (1940) suggested that there are intergrades of these subspecies in sympatric areas of southeastern Washington and Oregon, south central Idaho, and Utah. Kohl's conclusions were based on traditional morphological features of the “clasper” (basimere and telomere) and chaetotaxy of the outer surface of the hind tibia. These morphological features, and that of the aedeagus, have never been critically studied until now. The aedeagi of both taxa were examined and several consistent structures separate these closely allied species. The median dorsal lobe and apex of the sclerotized inner tube show little variation, although they are distinctly different among the sympatric populations and are consistent in peripheral populations. These characters are stable with little variation and their structure appears to be sufficiently different to potentially inhibit interbreeding that typically occurs where subspecies meet. These characters are valid distinguishing characters even when males of both species occur simultaneously on the same host. These newly reognized static characters of the aedeagus are illustrated. The lateral surface of the hind tibia is the most valid criterion for separation of females of the two species, although this cannot be determined with any degree of certainty. Spilopsyllus inaequalis interrupta is herein elevated to full specific status (Spilopsyllus interruptus) (Amended Status). Table 1 provides a resource for the terminology of various lobes and processes of the telomeric appendages of males of the superfamily Pulicoidea. Host and distribution records available in the literature are summarized in Tables 2 and 3.