Associative leaing is well documented in Hymenopteran parasitoids,where it is thought to be an adaptive mechanism for increasing successful host location in complex environments.Based on this leaing capacity,it has been suggested that providing prerelease training to parasitoids reared for inundative release may lead to a subsequent increase in their efficacy as biological control agents.Using the fruit fly parasitoid Diachasmimorpha krausii we tested this hypothesis in a series of associative leaing experiments which involved the parasitoid,two host fruits (tomatoes and nectarine),and one host fly (Bactrocera tryoni).In sequential Y-tube olfactometer studies,large field-cage studies,and then open field studies,na(i)ve wasps showed a consistent preference for nectarines over tomatoes.The preference for nectarines was retained,but not significantly increased,for wasps which had prior training exposure to nectarines.However,and again consistently at all three spatial scales,prior experience on tomatoes led to significantly increased attraction to this fruit by tomato-trained wasps,including those liberated freely in the environment.These results,showing consistency of leaing at multiple spatial scales,gives confidence to the many laboratory-based leaing studies which are extrapolated to the field without testing.The experiment also provides direct experimental support for the proposed practice of enhancing the quality of inundatively released parasitoids through associative leaing.