"Global warming often triggers the question if species response to a changing environment will enable them to persist. However species persistence is also dependent on species interactions. Relationships between tightly co-evolved species within communities are expected to be disrupted by thermal changes. An example of a co-evolutionary arms race is found in parasitoid insects, which develop in other arthropods to complete their larval development. The outcome of host-parasitoid interactions is known to depend on thermal regime but a full understanding of the effect of temperature requires insight into the underlying mechanisms. The proposed research will elucidate the effect of temperature on the interactions between the grain aphid host Sitobion avenae and its main specialist parasitoid, Aphidius rhopalosiphi. I will examine the thermal responses of the outcome of aphid parasitoid interactions in the pre-oviposition phase, when behavioural strategies largely determine parasitoid oviposition success, and in the post-oviposition phase, when the parasitoid is developing inside the aphid, as immunological interactions determine aphid or parasitoid survival. Most importantly, I will identify the underlying physiological mechanisms of behavioural and immunological responses that determine the outcome of the interaction. The combination of mechanistic and ecological approaches will provide understanding of the impact of temperature on interacting species that can be extrapolated to other systems."