none Laboratory studies on Microctonus aethiopoides, a parasitoid of Sitona discoideus, established that the development temperature thresholds of its egg and larval stages combined and pupal stage were 9 multiplied by 8 and 8 multiplied by 2 degree C, respectively. Additionally, the egg and larval stages combined and pupae required 144 multiplied by 4 and 125 multiplied by 4 day degrees ( degree D), respectively, for development. This species can complete two generations a year, when showing its usual aestivatory behaviour and when synchronized with that of S. discoideus. After arriving in an uncolonized district, populations of M. aethiopoides required c. three seasons to stabilize, after which the patterns of S. discoideus parasitism in different locations showed common features. Moderate April-July parasitism (c. 50%) in lucerne declined as the late instar larvae emerged from their weevil hosts and pupated during the winter. The near absence of parasitoid oviposition during the winter resulted in minimal parasitism in August-September.