In order to determine the existence of diff erentiation 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 diff erent 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 ). Th e 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 diff erent lengths. Th e morphometric data indicate the separation of the species in three groups: T. brasiliensis, T. melanica, and T. juazeirensis+T. brasiliensis macromelasoma . Th e 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.