In order to determine the existence of differentiation in the lengths of the testis follicles between three species and one subspecies of Triatoma a detailed morphometric analysis was carried out. Captures were performed at different sites where the species were described: Caicó, state of Rio Grande do Norte (T. brasiliensis), Petrolina, state of Pernambuco (T. brasiliensis macromelasoma), Juazeiro, state of Bahia (T. juazeirensis) and Espinosa, state of Minas Gerais (T. melanica). The records of the lengths of the testis follicles were submitted to statistic analysis. Results showed that all Triatoma studied have seven follicles in the testis, following the Triatominae pattern, which present different lengths. The morphometric data indicate the separation of the species in three groups: T. brasiliensis, T. melanica, and T. juazeirensis+T. brasiliensis macromelasoma. The obtained results are in agreement with other previous morphologic, ecologic, genetic, molecular, and phylogeographic studies, corroborating the importance of the morphometry on the testis follicles for taxonomic studies of triatomines.