Brazil has just been certificated by Pan American Health Organization as 'free of Chagas disease transmission due to Triatoma infestans'. During the early 1980s, this species of blood-sucking bug alone was considered responsible for approximately 80% of Chagas disease transmission. But it was not always so. The species originally abundant in houses of central and eastern Brazil was Panstrongylus megistus, which seems to have been progressively displaced from houses by T. infestans during the past century. Indeed, T. infestans seems able to displace other Triatominae in artificial environments. Recent studies suggest that it might simply be because T. infestans feeds more efficiently than its Triatominae competitors.