Triatoma brasiliensis sensu lato (s.l.), the main vector of Chagas disease in northeastern Brazil, is a species complex comprising four species, one with two subspecies (T. brasiliensis brasiliensis, T. brasiliensis macromelasoma, T. juazeirensis, T. sherlocki, and T. melanica), and each taxon displaying distinct ecological requirements. In order to evaluate the genetic relationships among nine T. brasiliensis s.l. populations from northeastern Brazil, we analyzed their mitochondrial cytochrome c oxidase subunit 1 sequences and suggested a PCR-RFLP assay to distinguish between T. b. macromelasoma and T. b. brasiliensis subspecies. All the specimens were morphologically identified as T. b. brasiliensis. The resulting phylogenies identified two major clades that are congruent with the geographical populations studied. Based on collection sites and in accordance with type-location, one clade was identified as the subspecies T. b. macromelasoma. The second clade grouped T. b. brasiliensis populations. Restriction endonuclease sites were observed in the sequences and used in PCR-RFLP assays, producing distinct fingerprints for T. b. macromelasoma and T. b. brasiliensis populations. The results suggest that these are different species and that gene flow occurs only among T. b. brasiliensis populations, possibly associated with human activity in the area. 1. Introduction About 28 million people live in areas at risk of Chagas disease, 11–14.5 million of whom are affected worldwide. Trypanosoma cruzi, the pathogen that causes Chagas disease, is found in most South American countries, representing an important cause of heart damage among the economically active population [1]. After a successful chemical control of Triatoma infestans (Klugi, 1834), the other main vectors of Chagas causing agent, Panstrongylus megistus Burmeister, 1835, Rhodnius prolixus Stal, 1859, and Triatoma brasiliensis sensu lato Neiva 1911. T. brasiliensis kept attracting considerable attention from local entomological surveillance. Triatoma brasiliensis sensu lato (s.l.), found in anthropogenic habitats and considered the main vector in northeast Brazil [2, 3], was recently found to be a species complex that includes T. b. brasiliensis, T. b. macromelasoma Galv？o, 1956, T. juazeirensis Costa & Felix, 2007, T. sherlocki Papa, Jurberg, Carcavallo, Cerqueira & Barata, 2002, and T. melanica Costa et al., 2006. These taxa exhibit wide phenotypic and morphological variability, displaying specific ecological requirements and chromatic patterns [4]. In this respect, accurate species
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