Circumscription of the sclerolobii group of Amblycerus Thunberg (Coleoptera, Chrysomelidae, Bruchinae) with descriptions of four new species and a revision of the species groups of the genus.

The seed-beetle Amblycerus Thunberg, 1815 the second most diverse genus of Bruchinae (Chrysomelidae) in the Western Hemisphere, is organized into groups of species, as many others in the subfamily. The main objective of this work is to delimit the group sclerolobii, here established as composed by five described species, A. sclerolobii Ribeiro-Costa, 2000, A. kingsolveri Ribeiro-Costa, 1993, A. marinonii Ribeiro-Costa, 1993, A. manauara Ribeiro-Costa, 2000, A. tachigaliae Kingsolver, 1976 and four new species: A. biacutus Ribeiro-Costa, sp. nov., A. falcorostrus Ribeiro-Costa & Morse, sp. nov., A. morsei Ribeiro-Costa, sp. nov. (type localities: Brazil: Amazonas, Manaus) and A. truncatus Ribeiro-Costa, sp. nov. (type locality Brazil: Mato Grosso, Sinop). Therefore, including these new species 70 Brazilian species of Amblycerus were recorded. Amblycerus bicolor (Pic, 1927) previously considered to belong to this group is excluded and placed as incertae sedis. The sclerolobii group is distributed mainly in the Brazilian Amazonia biome, consuming Tachigali Aubl., Dinizia Ducke, and Stryphnodendron Mart. seeds (Fabaceae). Diagnoses are presented for this group and for ten species (including A. bicolor), and descriptions for the four new ones, an identification key for the nine species, colored photographs of external morphology, and detailed male genitalia illustrations for all the species studied. Due mainly to previously broad contributions on the taxonomy of Amblycerus that resulted in many species groups, we also present a revised study of this intrageneric taxonomic level. From 37 species groups now we update to 32 groups with a total of 96 species assigned to them. Finally, a detailed systematic study of some specific groups is also suggested before mergence.