The structures of the exoskeleton and genitalia of bruchines preying on Senna neglecta (Vogel) H.S. Irwin and Barneby seeds were studied. Three new species are described and S. neglecta is recorded as a new host plant for the subfamily. The six bruchine species associated with S. neglecta are Amblycerus hoffmanseggi (Gyllenhal 1833) (Amblycerini), Acanthoscelides multimaculatus sp. nov., Sennius bondari (Pic 1929), Sennius nappi Ribeiro-Costa and Reynaud 1998, Sennius margarete sp. nov. and Sennius ricardo sp. nov. (Bruchini). Sennius bondari is the most polyphagous species, while Sennius margarete sp. nov. and Sennius ricardo sp. nov. are currently only known from S. neglecta. Descriptions, redescriptions or diagnoses are presented, including revised characters based on electron microscope images of the denticles at the base of the elytra striae, and the lateroventral carina of the hind tibia. An identification key, illustrations, a list of host plants and geographical distribution records are also inclu...