The “kissing bugs,” Triatoma dimidiata (Latreille) and Bhodnius prolixus (Stål) (Reduviidae: Triatominae) are major vectors of Chagas disease in Central and South America. To further uncover the attraction to certain host cues by these vectors at long and short distances from their host, the behavioral responses of two life stages (fifth-instar nymphs and adult males) of these two species to different known or suspected attractants, alone or in combination, were investigated. Tests were done using short- and long-range environments, namely, a four-port olfactometer and a long-range artificial chamber designed to mimic the insect's natural habitats. In single-attractant trials, heat alone and CO₂ alone were found to be more attractive than selected chemicals. In multiple-attractant trials, both species and life stages were attracted at short distances, and a statistically significant synergistic increase in attraction was observed in long-distance multimodal tests. Lures containing CO₂ were the most effective attractants at both long and short distances. R. prolixus adult males were significantly less attracted to several lure combinations than the nymphs of either species, perhaps because adults were more motivated to seek mates than feed. Our findings suggest that although the triatomine bugs may be capable of detecting odorants and heat sources at short distances, their ability to locate a host over a long distance is best aided by the presence of a CO₂ plume.