For many years the causative agent of Chagas' disease has been found commonly in many individuals of known insect vectors, less abundantly in mammalian reservoirs and least commonly in man. This contribution brings together apparently unrelated data which demonstrates one explanation of the abundance of naturally infected insect vectors and the greater prevalence in mammals other than man of Trypanosoma cruzi. The ability of this parasite to persist in a viable state in dead or immobilized insect vectors is an important factor in maintaining a large rodent reservoir population since these mammals feed on insects and acquire the infection in that way.
As previously reported by the writer (Wood, 1942b), the persistence of developmental stages of Trypanosoma cruzi Chagas was noted in the feces and body fluids of bugs many days after death. Additional data are presented here on the persistence of Trypanosoma cruzi in its crithidial and trypanoform stages in naturally-dying and cyanide-treated cone-nosed bugs (Triatoma spp.).