After a similar work, done in 1955, comprehending the period 1944-1951, variations of the evolutive forms of the T. infestans and P. megistus incidence in Bambuí, M.G. 22,581 samples of T. infestans and 2,694 of P. megistus, captured in nature by the department of the I.O.C in Bambuí were analized. The monthly variations of the different evolutive forms for both species are, in a general way, the same found by Dais in a previous work. The small percentage of association between the two species in natural lodgings, suggests, the hypothesis of a biological antagonism among them. Observations make as infer that, in Bambuí, the p. megistus presents perhaps two generations. Comparing the evolution grafhics, before and after the prophyllatical work in Bambuí, in 1956 and 1957 one verifies that there does not seem to have occurred significant changes in the behaviour of the above species due probably to new contigents of insects, of similar evolution, prodeeding from the near by communities or from "residual foci" in Bambuí, in which the BHC aspersions did not influence directly in the evolution. Regarding the indexes of infection by the S. cruzi, they are similar for both species (3.21 for the T. infestans and 3.25% for the P. megistus). The adult forms are more infected and, throughout the yer, there is no great variety of positiveness in diferent months. There has been a significant reduction of the prophylatical works, with little increase of the P. megistus' indexes, motivated perhaps by the dwelling invasion occurred by this species.