Triatoma patagonica is highly variable regarding the distribution of the pattern elements on the corium and connexivum; the dark pattern elements seem to be more extensive and intensive in the eastern, more humid portion of its range, and become more reduced in the semiarid western portion of Argentina (Lent & Wygodzinsky 1979).
Holotype of Triatoma gallardoi deposited at MACN (Museo Argentino de Ciencias Naturales "Bernardino Rivadavia”, Buenos Aires, Argentina (Bachmann 2012).

This species has been found naturally infected with Trypanosoma cruzi. It is atracted to light. It has been found in peridomestic habitats (chicken houses and rabbit coops); and sylvatic habitats such as under bark or rocks, and in burrows of Microcavia australis (Lent & Wygodzinsky 1979).