This monograph is a compilation of original and recent research on southern South American stag beetles (Coleoptera: Scarabaeoidea: Lucanidae). In the study area, the wholly endemic stag beetle fauna includes 31 species in three subfamilies. A key to genera of southern South American Lucanidae is provided. Updated information on genera that have been recently revised is included. All species are redescribed and keys are provided in English and Spanish when appropriate.
In the study area, the subfamilies Aesalinae and Lampriminae are represented by three species of Hilophyllus Paulsen and Mondaca (Ceratognathini) and one species of Streptocerus Fairmaire (Lamprimini), respectively. The monogeneric tribe Streptocerini Kikuta is placed into synonymy with Lamprimini, new synonymy.
In the Lucaninae, species from two tribes are distributed in southern South America, the Chiasognathini and Sclerostomini. The Chiasognathini of the region includes seven species of Chiasognathus Stephens. The Sclerostomini of the Lucaninae are treated in the following genera: Apterodorcus Arrow (two species), Caenolethrus Grossi and Paulsen (one species), Chileistomus Weinreich (one species), and Sclerostomulus Weinreich (two species).
In addition, the genus Pycnosiphorus Solier of the Sclerostomini is revised, and morphological and molecular phylogenetic data indicate that two distinct groups are present that are here treated as two genera: Pycnosiphorus that are fully-winged, and Erichius Maes that are flightless (brachypterous). The genus Pycnosiphorus now contains two species, P. lessonii (Buquet) and P. philippi (Westwood), the former with five subspecies, one of which is proposed as new (P. lessonii ugartei, n. ssp.). New combinations include: P. lessonii elongatus (Deyrolle) and P. lessonii mandibularis (Solier). A neotype is designated for Sclerostomus elongatus. Lectotypes are designated for Dorcus lessonii, D. mandibularis, Sclerostomus marginipennis Deyrolle, and S. philippi. New synonymies include: P. germaini Numhauser is synonymized with P. lessonii mandibularis and P. westwoodi Numhauser is synonymized with P. philippi.
The subgenus Erichius is elevated to generic status and contains 12 species, including one new species, E. zabulostictus. One species, E. darwinii Hope, n.comb., is valid and is removed from synonymy with E. femoralis (Guérin-Méneville), n.comb. Other new combinations include: E. brevicollis (Benesh), E. caelatus (Blanchard), E. calverti (Nagel), E. costatus (Benesh), E. fairmairii (Parry), E. fasciatus (Germain), E. franzae (Weinreich), E. virgatus (Nagel), and E. vittatus (Eschscholtz). Two new combinations result from the reduction to subspecific status of E. fairmairii arriguttii (Weinreich) and E. vittatus magnificus (Benesh). The identities of E. fairmairii (Parry) and E. vittatus (Eschscholtz) had been confused with other taxa in the literature and are corrected. Neotypes are designated for Dorcus leiocephalus Solier, D. pallidocinctus Fairmaire and Germain, D. rouleti Solier, D. rufipes Solier, D. rufifemoralis Curtis, Lucanus vittatus Eschscholtz, and Sclerostomus calverti Nagel. Lectotypes are designated for D. femoralis Guérin-Méneville, D. spinolae Solier, L. caelatus Blanchard, L. rubrovittatus Blanchard, L. variolosus Hope, Sclerostomus fairmairii Parry, and S. virgatus Nagel. New synonymies include: D. rufipes, D. leiocephalus, D. spinolae, and D. modestus Philippi (all synonyms of E. darwinii); D. pallidocinctus (synonymized with E. femoralis); and D. rouleti (synonymized with E. vittatus). The following subgeneric names are synonyms of Erichius: Epipedus Solier, Calvertius Maes, and Neoepipedus Ozdikmen and Turgut.