Triatoma guazu Lent and Wygodzinsky and Triatoma williami Galvão, Souza, and Lima (Hemiptera: Triatominae) are found in human dwellings and are potential vectors of the protozoan Trypanosoma cruzi, the etiological agent of Chagas disease. Triatoma guazu was described based solely on a single female specimen, from the municipality of Villarica, Guairá Department, Paraguay, and posteriorly, a male from Barra do Garças, Mato Grosso, Brazil was described and designated as the allotype of this species. Triatoma williami is found in the central-west of Brazil between Goiás, Mato Grosso, and Mato Grosso do Sul. However, the taxonomic "status" of these species is questioned. Previous studies indicate the lack of isoenzymatic diagnostic loci, morphometric similarity, low genetic divergence, and close evolutionary relationship of these species. In this study, we compared the morphology, morphometry, and mitochondrial DNA fragments of the populations of the two species. The morphological diagnostic characteristic among these species is the difference in the connexivum spots pattern, which has been recognized as a phenotypic variation that exists among populations resulting from ecological diversity. Furthermore, our analysis also revealed the morphometric similarity and low genetic divergence between these species. Therefore, in the present paper, we formally propose T. guazu as a junior synonym of T. williami.
Keywords: Triatominae; geometric morphometry; mitochondrial DNA; morphological analysis; synonym.