The post-embryonic development, the productivity of the pupae, the rate of parasitism and the sexual ratio of Nasonia vitripennis (Walker) reared in pupae of Cochliomyia macellaria (Fabricius) were studied. Different densities of the parasitoid were used (proportions 1:1, 2:1, 3:1, 4:1, and 5:1) with exposition of 72 hours. Nulliparous females originating from the stock colony were individualized in test tubes covered with hydrophobic cotton and containing the host pupae. Each treatment was constituted by 10 repetitions. After the exposition, the wasps were discarded and the host pupae were individualized in test tubes until the emergency of the adults of C. macellaria or N. vitripennis. Samples of host pupae not exposed to parasitism and receiving the same experimental treatment were used as control. The post-embryonic period was significantly shorter in the proportion of 2:1 (13,73 days) and longer in the relation of 5:1. The peaks of emergence occurred in the 14th day after the exposition of the parasitoid to the host in all relations, except for the relation of 4:1(13rd day). The productivity of N. vitripennis does not vary significantly among the different proportions. As the number of parasitoids grows, its post-embryonic development gets slower and the sexual ratio of males grows up. The rate of parasitism showed a decrease when the host was exposed to five parasitoids.
biological control; wasp; fly; parasitism
