RESUMO: The South American genus Aclopus Erichson, 1835, is herein treated in a taxonomic synopsis. Aclopus wuenschei Ohaus, 1912 syn. nov. is proposed as a junior synonym of Aclopus vittatus Erichson, 1835, and three new species of Aclopus are described: Aclopus extrema sp. nov., Aclopus frieirocostai sp. nov. and Aclopus godinhorum sp. nov. Notes on the natural history of A. frieirocostai are also given. Furthermore, Allsoppaclopus gen. nov. is described to include Allsoppaclopus intermedius (Blanchard, 1850) comb. nov. and Allsoppaclopus dzupi sp. nov. Diagnoses, illustrations, distribution maps and identification keys for Aclopus and Allsoppaclopus species, as well as for the genera of Aclopinae, are also provided.