"The type locality for this species is in Jujuy Province, locality not specified (Knight & Stone, 1977). Before the monograph of Arnell (1973), this species and its subspecies, falco (now a synonym of janthinomys) were thought to be extensively distributed in Central and South America. Under the present concept, spegazzini (s. str.) is confined to eastern and southern Brazil, eastern Bolivia, Paraguay, and northern Argentina. This species extends farther south in Argentina than any other Haemagogus. A synonym of spegazzini, Haemagogus uriartei Shannon & Del Ponte, was the name used by Duret (1950c, 1951b, 1952) and Castro et al. 1959 (1960) for this species. It was synonymized under spegazzini by Martínez et al. (1961a)." (Mitchell & Darsie, 1985).

Disease relations: Haemagogus janthinomys effectively transmits the Mayaro virus (Muñoz & Navarro, 2012).

Larvae have been collected in water bodies of natural environments such as holes in trees and rocks (Lane, 1953). In Argentina, the species has been reported breeding in tree holes in Salta, Córdoba, Chaco (Campos & Gleiser, 2016; Stein et al., 2012), and La Pampa (Obholz et al., 2020) provinces. In the latter study, Prosopis caldenia has been recorded as a new host plant to Haemagogus spegazzinii breeding sites (Obholz et al., 2020), as well as Prosopis nigra (Alvarez et al., 2024). Females do not have anthropophilic behavior and have been captured during daylight hours (Campos & Gleiser, 2016; Díaz Nieto et al., 2020).