Scanning electron microscopy of the final phase of the life cycle of Trypanosoma cruzi in the insect vector.

Scanning electron micrographs showed that both epimastigotes and metacyclic trypomastigotes of Trypanosoma cruzi are attached by the flagellum to the epithelium of the rectal gland of Triatoma dimidiata. The flagellates tended to cover the surface of the gland and there was a marked predominance of epimastigotes with a round posterior end. Reproduction and metacyclogenesis seem to take place in situ, the latter apparently by twisting and elongation of the epimastigotes. Metatrypomastigotes remain attached for some time, probably by a weaker mechanism which easily allows them to loosen, facilitating expulsion with the urine or feces.