While feeding on infected animals, the true bugs of the subfamily Triatomidae of the family Reduviidae, suborder Hemiptera) ingest the trypomastigote in the human host’s blood. Dividing and transforming in the gut of the bug, the T cruzi appear in the hindgut as metacyclic trypomastigotes, which are infective to humans. Once infected, the bug remains so for life. No sexual cycle occurs in trypanosomes.

Those reduvids that occupy human dwellings are strong vectors of Chagas disease. Rhodnius prolixus in Central America, Colombia and Venezuela. Triatoma infestans in much of South America and Panstrongylus megistus in Brazil are adapted to houses.