Description of fifty-one new species and new taxonomic arrangement for the E. sexdens group of the subgenus Edessa (Heteroptera, Pentatomidae, Edessinae, Edessa)

Within the subfamily Edessinae, Edessa Fabricius, 1803 is the genus with the most nomenclatural and taxonomic issues, basically related to the large number of poorly described species and the large number of new species. Furthermore, for many groups of morphologically similar species, certain names are used as “tag names”, adding to confusion and misidentification. The genus Edessa has been studied in small groups of species, either informal morphological groups within the genus or formal subgenera. Recently the nominal subgenus was revised and delimited, including the group E. sexdens. The E. sexdens group is diagnosed by a combination of characters such as anterior arms of metasternal process with excavated apex; connexival segments with a pair of dark spots; ventral surface of abdomen elevated medially; presence of a shallow rounded excavation near each spiracle; pygophore with union of dorsal rim and posterolateral angles with a groove, superior processes of the genital cup laminar, oblique to the paramere and continued ventrally by a carina; and paramere with three lobes. The biology of species in this group is almost unknown and most species have been collected in the Amazon region, particularly in the Brazilian Amazon. This group is the largest, in number of species, within the subgenus Edessa, presenting a surprising number of new species. In this article, fifty-one species new to science are described and Olbia magnifica Pirán, 1958 is transferred to Edessa. The composition of the E. sexdens group is updated to 74 species (23 previously described and 51 described here). The identification key to the species of the E. sexdens group is updated, and maps with the distribution of the new species are presented.