none The effects of temperature on growth and development of the cabbage butterfly, Pieris rapae , and three wasp parasites: Apanteles rubecula, A. glomeratus and Pteromalus puparum in Vancouver, Canada, and Canberra, Australia, are examined. The authors compare the estimates of temperature threshold for development and the number of degree-days above this threshold required to complete development for the immature stages of all species in both localities. Developmental patterns of both the host and its parasites differ between localities. Within the range of temperatures likely to be experienced during the host's breeding season, Australian parasites have longer generation times thantheir host at low temperatures and shorter generation times at high temperatures. Canadian parasites have shorter generation times, relative to the host, at all temperatures. This may be necessitated by the shorter breeding season available to the Canadian parasites. Besides temperature, parasite development is affected by host size and, in the gregarious species, parasite density. Host larval development is retarded by both Apanteles .