New species, new combinations, and morphological notes of South American Ambrysinae (Heteroptera: Naucoridae) Author Rodrigues, Higor D. D. 0000-0002-9649-4142 Laboratório de Entomologia, Instituto Oswaldo Cruz, Fundação Oswaldo Cruz, Rio de Janeiro, RJ, Brazil. higorddr@gmail.com Author Canejo, Rafael P. R. 0000-0003-4296-8936 Laboratório de Entomologia, Instituto Oswaldo Cruz, Fundação Oswaldo Cruz, Rio de Janeiro, RJ, Brazil. rafaelcanejo17@gmail.com Author Sites, Robert W. 0000-0002-3895-813X Enns Entomology Museum, Division of Plant Sciences, University of Missouri, Columbia, MO, United States. sitesr@missouri.edu text Zootaxa 2024 2024-05-06 5447 2 199 224 http://dx.doi.org/10.11646/zootaxa.5447.2.3 journal article 10.11646/zootaxa.5447.2.3 1175-5326 11119501 F1BE770F-C904-4320-89F5-63733611E994 Australambrysus plax (La Rivers, 1967) species complex Discussion. The A. plax species complex is diagnosed by having the propleura tightly appressed to the probasisternum and prosternellum, thereby concealing part of the prosternellum—although this condition also occurs in the subgenus Ambrysus ( Syncollus ) La Rivers, 1965 , from North America ( Sites 2023a ). In addition to this feature, the species in this complex also share: propleuron shagreened throughout, except a thin, glabrous band in the lateral margin ( Figs. 1B , 2B , 3B ); ventrally entirely golden brown, with dense pile of fine hairs, and two glabrous median stripes on abdominal sterna IV–V; at least the posterolateral corners of abdominal segments IV–VI spinose; absence of an accessory genitalic process of male abdominal tergum VI ( Figs. 2C , 3D ); and the male phallosoma with ventral endosomal lobes membranous ( Figs. 2G , 3H ). It is important to note that the diagnostic features listed above are not necessarily exclusive to the complex. Australambrysus acutangulus ( Montandon, 1897b ) and A. fraternus ( Montandon, 1897b ) are known only from the male holotypes , which have not been dissected; however, we suspect they have the same features as the other species in the complex. We have other probable Brazilian new species from this complex, which are easily differentiated by the male genitalia and the female abdominal sterna; however, to minimize the risk of describing them as possible future synonyms, the genitalia of A. acutangulus and A. fraternus should be described first.