RESUMO: Arnaudius Grossi & Bartolozzi, 2011 is a stag beetle genus endemic to Peru, currently comprising three described species. In this study, we describe a fourth species for the genus, Arnaudius monnei Soares & Grossi sp. nov., based on two specimens collected in Machu Picchu, Peru. This new species shares all the diagnostic features of the genus, particularly those related to the male genitalia, the most unambiguous. The description of this new species calls attention to the unknown diversity of Lucanidae in the Tropical Andes, a region with high endemism, but which still remains largely undersampled. The new species is described, illustrated, and compared with the other species of the genus. Additionally, we provide an updated identification key for the males of the species of Arnaudius and a known distribution map.
doi: https://doi.org/10.11606/1807-0205/2026.66.special-issue-1.021