Whether to invest in current or future reproduction is an important trade-off in life history evolution. For insect parasitoids, this trade-off is determined, among other factors, by the decision whether to search for hosts (immediate gain of fitness) or food (delayed fitness gains). Although host searching has been well studied, food sources, cues that parasitoids use to search for food and how insects modify their feeding behaviour have not. To address these questions, we investigated the food- and host-searching decisions made by the parasitoid Venturia canescens in both laboratory (olfactometer experiments) and field conditions (choice experiments). The wasps detected chemical cues associated with food, as well as those associated with hosts, and moved towards one or the other according to their nutritional state. Females used as food sources the same fruits that harboured hosts and detected the olfactory cues that would direct them to these fruits. Field results were consistent with those obtained in the laboratory. By integrating responses to infochemicals related to host and food, V. canescens might reduce the costs associated with food searching, so that more time and energy can be allocated to foraging for hosts. This behaviour should result in an adaptive advantage over parasitoids that incur additional costs by searching for hosts and food in different locations. 2005 The Association for the Study of Animal Behaviour. Published by Elsevier Ltd. Ephestia kuehniella (Pyralidae) : Host Venturia canescens (Ichneumonidae) : Parasite Sensory reception; Nutrition; Evolution; Parasites diseases and disorders; Parasites; Insect parasites; Hosts; Insect hosts; Ecology; Population dynamics Ephestia kuehniella; Hymenopteran parasites; Investment in host vs food seeking; trade-offs; integration & influences; Venturia canescens Venturia canescens; Chemoreception; Diet; Honey; Energy budget; Metabolic reserves; Natural selection; Fitness; Lepidopteran hosts; Investment in host vs food seeking; trade-offs; integration & influence of nutritional state; Ephestia kuehniella; Survival none