Abstract
Thirty-one species of Nearctic Perlesta Banks, 1906 (Plecoptera: Perlidae) are recognized. A new species is described from western Arkansas and eastern Oklahoma, USA, Perlestasublobata South & DeWalt, sp. nov., from the adult male, adult female, and egg. Perlestasublobata males are differentiated from other congeners by a combination of a prominent ventral caecum and a distinct dorsal extension of the lateral sclerites of the aedeagus. A preliminary molecular phylogenetic hypothesis is proposed for Perlesta based on 17 congeners and three outgroup taxa using partial mitochondrial cytochrome c oxidase subunit I sequence data. Illustrations, stereomicroscope images, and scanning electron micrographs support the description and comparison to other Perlesta.