"Martínez et al. (1961a) named three taxa in Argentina as distinct, Haemagogus capricornii janthinomys, Haemagogus capricornii falco and Haemagogus capricornii petrocchiae. Arnell (1973) made significant changes by removing janthinomys as a subspecies of capricornii and raising it to specific rank. The other two taxa were synonymized under janthinomys. another synonym of this species is Haemagogus spegazzini falco, the name used previously for a widely distributed taxon and a principal vector of sylvatic yellow fever (Arnell 1973). The record for janthinomys from Tucumán by Carcavallo & Martínez (1968a) (as Haemagogus capricornii petrocchiae) is indicated only by a map, Fig. 63." (Mitchell & Darsie, 1985).

Disease relations: the species is considered the main selvatic yellow fever vector species (Consoli & de Oliveira, 1994), and was involved in several outbreaks of Yellow Fever virus (Flaviviridae: Flavivirus) in Central and South America (Chadee et al., 1992; Degallier et al., 1992; Muñoz-Rodriguez et al., 2010; Vasconcelos et al., 1997), by Mayaro Virus (Togaviridae: Alphavirus) in Brazil (Holch et al., 1981) and Venezuela (Muñoz & Navarro 2012).

Haemagogus janthinomys is specialists, that is, they use phytotelmata as their only breeding site (Obholz et al., 2020).
Females were captured in peri-urban environments.