Species of Perditorulus can only be identified in the male sex, females are currently not possible to identify. The males are identified through the appearance of the phallobase, one part of the genitalia. To be able to examine the phallobase slides of the apical part of the gaster must be prepared, see Hansson (1996) how to do this. Initially the males can be divided into two groups, the ones with a narrow scape (scape at least 3.2X as long as wide in lateral view) and the ones with a wide scape (scape at most 2.9X as long as wide in lateral view). After this division characters in the phallobase are the only means by which species can be identified. The appearance of the phallobase is distinct for each species, and the quickest way to identify species is simply to compare the specimen with the illustrations of the phallobases. There are links to two pages with illustrations of the phallobases, one for species with a narrow scape, and one for species with a wide scape. To see a larger illustration double-click on the thumbnail picture. There is no key included here for the identification of the species. Hansson (2004) includes a dichotomous key for the species. Here is a link to the fact sheets for the species.