Immature Instars of Three Species of Rhodnius (Hemiptera, Reduviidae, Triatominae): Morphological and Morphometric Studies

Abstract 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.