ABSTRACT The classic episode of biological invasion: Cochliomyia macellaria (Fabricius, 1775) versus Chrysomya megacephala (Fabricius, 1794) (Diptera: Calliphoridae) - evaluation of the biotic potential. The biotic of the native fly Cochliomyia macellaria and the exotic Chrysomya megacephala was compared, through the reproductive capacity and longevity. The experiment took place in a climatized chamber, with four repetitions of 15 grouped couples of each species. The posture, egg mass weight, and death of individuals were observed daily. C. macellaria showed an average of longevity of 27.72 days while in C. megacephala the average was 41.96 days. The egg mass weight average per repetition was 0.58 g and 1.22 g, respectively. These results give a better understanding about the population dynamics of these species in nature.