VARIABILITY IN THE DEVELOPMENT OF CEREAL APHID PARASITOIDS AND HYPERPARASITOIDS IN OCEANIC REGIONS AS A RESPONSE TO CLIMATE AND ABUNDANCE OF HOSTS

Experiments were conducted to understand how parasitoids and hyperpara sitoids of cereal aphids in oceanic regions survive the periodic disap pearance of their hosts. We recorded the number of parasitoids and hyp erparasitoids emerging from mummies collected in summer on winter whea t and corn and in winter on cereal volunteers. In addition, we studied the duration of both summer and winter development of Aphidius rhopal osiphi De Stefani-Perez, the main parasitoid species of cereal aphids. In summer, interruption in development occurred in primary parasitoid s which resulted in a longer development time (up to 4 m). These inter ruptions were fairly infrequent but they did ensure the survival of pa rt of the population when there was a large decrease or disappearance of the aphid population. A longer duration of summer development also was recorded in a few hyperparasitoids. In winter, an important variab ility in the length of the development of primary parasitoids was note d which reflected their adaptive closeness to the aphid cycle. All hyp erparasitoids studied here had long interruptions in their development and emerged only at the end of winter.