Chagas disease (CD) is a neglected illness affecting approximately seven million individuals, with vector transmission occurring via triatomine bugs. The Rhodniini tribe comprises 24 species, grouped into the Rhodnius and Psammolestes genera. Given the importance of accurately identifying CD vectors, the taxonomy of Psammolestes spp. was revisited using morphological and morphometric data. Specimens of P. tertius, P. coreodes, and P. arthuri were collected, and the morphological characteristics of the head, thorax, abdomen, and eggs were analyzed. Morphometric studies of eggs were also conducted. Dichotomous keys allowing for the differentiation of Psammolestes spp. were elaborated based on adult insect and egg morphological characteristics. Through these studies, it was possible to differentiate the three Psammolestes species and confirm that this genus should not be classified under the Rhodnius genus, contributing to Rhodniini taxonomy.

Background: Among the 18 genera of the Triatominae subfamily, three stand out for their diversity and epidemiological importance:Triatoma,Panstrongylus, andRhodnius.Rhodniusincludes 21 species that can transmitTrypanosoma cruzi(the etiological agent of Chagas disease, also known as American trypanosomiasis) andTrypanosoma rangeli. TheRhodnius prolixuscomplex comprises seven species, includingRhodnius marabaensis,Rhodnius prolixus, andRhodnius robustus, which occur in the northern region of Brazil. Since both adults and immatures can carryT. cruzi, in this study the five nymphal instars of the three species mentioned were dorsally characterized.Methods: Using microscopy, morphometrics, and geometric morphometrics, the present work measures and describes the morphological characters of the five nymphal instars ofR. marabaensis,R. prolixus, andR. robustus.Results: The study enabled the characterization of all five nymphal instars, as well as the distinction between the three species in each of their instars.Conclusions: The morphological, morphometrics of the head, thorax, and abdomen and geometric morphometrics studies of the head enabled the specific distinction of these three species in all five instars.Graphical

Background: Among the 18 genera of the Triatominae subfamily, three stand out for their diversity and epidemiological importance: Triatoma, Panstrongylus, and Rhodnius. The genus Rhodnius includes 21 species that can transmit Trypanosoma cruzi (the etiological agent of Chagas disease, also known as American trypanosomiasis) and Trypanosoma rangeli. The Rhodnius prolixus complex comprises seven species, including Rhodnius marabaensis, Rhodnius prolixus, and Rhodnius robustus, which occur in Northern region of Brazil. Since both adults and immatures can carry T. cruzi, in this study the five nymphal instars of the three species mentioned were dorsally characterized. Methods: By means of light microscopy, morphometrics and geometric morphometrics, the present work measures and describes the morphological characters of the five nymphal instars of Rhodnius marabaensis, Rhodnius prolixus, and Rhodnius robustus. Results: The study allowed the characterization of all the five nymphal instars, as well as the distinction between the three species in each of their instars. Conclusions: The morphological, morphometrics of the head, thorax, and abdomen and geometric morphometrics studies of the head enabled the specific distinction of these three species in all the five instars.