Seven species of the Bolboderini tribe belonging to the genera bolbodera, Belminus, Microtriatoma and Parabelminus, two of them found naturally infected with Trypanosoma cruzi, were analysed and compared emphasizing eight structures of the male external genitalia: median process of pygophore (PrP), conjunctiva process (PrCj), pedicel (EP1b), endosoma process (PrEn), struts (SPh), phallosoma (Ph), medium bridge (PrG) and vesica (V). Microtriatoma trinidadensis (Lent, 1951) and M. borbai Lent & Wygodzinsky, 1979 have shown a structural morphological aspect similar to Parabelminus yurupucu Lent & Wygodzinsky, 1979 and P. carioca Lent, 1943 differing clearly from Belminus peruvianus Herrer, Lent & Wygodzinsky, 1954, B. herreri Lent & Wygodzinsky, 1979 and Bolbodera scabrosa valdés, 1910, not only by the absence but by the shape of some structures. These comparative observations confirm the affinity between Microtriatoma and Parabelminus and their relations with Belminus and Bolbodera.