Triatoma brasiliensis is one of the most important vectors of Chagas
disease in the semiarid zone of the northeast of Brazil. Intraspecific
morphological and behavioural variation has been reported for different
populations. Results for four distinct populations using eight isoenzymes
are reported here. The literature describes three subspecies: T.
brasiliensis brasiliensis Neiva, 1911; T. brasiliensis melanica
Neiva & Lent, 1941 and T. brasiliensis macromelasoma Galvao, 1956.
These subspecies differ mainly in their cuticle colour pattern and were
regarded as synonyms by Lent and Wygodzinsky (1979). In order to evaluate
whether the chromatic pattern is a morphological variation of different
melanic forms within T. brasiliensis or due to interspecific
variation, field collections were performed in localities where these three
subspecies have been described: Caico (Rio Grande do Norte), the
type-locality for T. b. brasiliensis; Petrolina (Pernambuco) for
T. b. macromelasoma and Espinosa (Minas Gerais) for T. b.
melanica. A fourth distinct chromatic pattern was found in Juazeiro
(Bahia). A total of nine loci were studied. Values of Nei's genetic
distance (D) were calculated. T. b. brasiliensis and T. b.
macromelasoma are the closest populations with a D=0.295. T. b.
melanica had a D } 0.537 when compared to the others, a distance in the
range of interspecific variation for other triatomine species.
