Nyssorhynchus triannulatus is considered a complex of three species: Nyssorhynchus triannulatus s.s., Nyssorhynchus halophylus, and Nyssorhynchus triannulatus C due to the morphological variability in the male genitalia, eggs and larvae, and isoenzymes (Silva-do-Nascimento et al. 2006). Differences in distribution patterns, ecology, and behavior have been reported (Silva-do-Nacimiento & de-Oliveira 2002, Rosa-Freitas et al. 2007).
There have been 4 subspecies described under this species, bachmanni Petrocchi, chagasia Galvao, davisi Paterson and Shannon and perezi Shannon and Del Ponte. All have been synonymized with the type species which was discussed by Faran (1980). The type localities for 3 of them are in Argentina as follows: bachmanni - described from a series collected in Corrientes, Entre Ríos and Formosa provinces; davisi - Tres Pozos, Embarcación, Salta province; perezi - Santa Bárbara, Tucumán province (Mitchell & Darsie, 1985).
Disease relations: Anopheles triannulatus is considered a local or secondary vector of malaria in Brazil (Oliveira-Ferreira et al. 1990, de Arruda M et al. 1986, Tadei et al. 2000); an important vector in Peru (Aramburú et al. 1999); and it was implicated as the possible vector during a malaria epidemic in Venezuela (Benarroch 1931).
Immature stages are found in large bodies of water such as lagoons, river backwaters, and man-built dams, always well exposed to light and with abundant floating vegetation (Forattini, 2002). Although the behavior of females is exophilic and zoophilic, females have been framed in the transmission of human malaria, since they have endophilic and anthropophilic behavior in areas of Venezuela (Forattini, 2002).