Triatomine bugs are vectors of Trypanosoma cruzi, the etiologic agent of Chagas disease, a devastating disease that disables and leads to the death of many people in Latin America. In this review, factors from the insect vector are described, including digestive enzymes, hemolysins, agglutinins, microbiota and especially antimicrobial factors, which are potentially involved in regulating the development of T. cruzi in the gut. Differential regulation of parasite populations shows that some triatomine defense reactions discriminate not only between molecular signals specific for trypanosome infections but also between different strains of T. cruzi. Copyright © 2010. Published by Elsevier Ltd.