Nine new species of pselaphine rove beetles from the southeastern USA are described within four euplectite genera: Rhexius amyae Owens and Carlton, new species; Rhexius jaceus Owens and Carlton, new species; Pseudactium jaitlynum Owens and Carlton, new species; Actium riobuffaloensis Owens and Carlton, new species; Bibloplectus baylessae Owens and Carlton, new species; Bibloplectus bossartae Owens and Carlton, new species; Bibloplectus faulknerensis Owens and Carlton, new species; Bibloplectus ferroi Owens and Carlton, new species; and Bibloplectus kylei Owens and Carlton, new species. A single new synonymy is noted in the genus Conoplectus Brendel, 1888: Conoplectus acornus Carlton, 1983 with Conoplectus canaliculatus (LeConte, 1849), new synonymy. Regional checklists of the species in each genus are provided, and new species are integrated into previously published keys and supported by illustrations of diagnostic characters. All specimens in this study were obtained from the pinned collection of the Louisiana State Arthropod Museum (LSAM, Louisiana State University, Baton Rouge, Louisiana, USA). Evaluation of museum holdings revealed substantial taxonomic coverage of the supertribe regionally: 4,823 specimens were documented, representing 74 of the 87 species and 25 of the 25 genera previously known from the southeastern USA. This publication highlights the inherent value of regionally focused arthropod museums as unique repositories of faunal elements from their area of coverage.