The expected success of Chagas disease control programs in the Southern Cone countries relied on the assumption that Triatoma infestans, the main domestic vector, did not maintain silvatic foci except in the Cochabamba valley in Bolivia. Recent fieldwork revealed that wild populations of this vector are much more widespread throughout Bolivia than previously thought. Therefore, it is important to find out whether these silvatic populations could jeopardize control efforts in Bolivia, and to investigate their possible occurrence in neighboring regions of Paraguay and Argentina.