Plant-herbivore-parasitoid systems include over half of all known species. These interactions are often chemically mediated and can be used to understand complex biotic communities. Increasing temperatures over the next century are predicted to disrupt plant-insect interactions. Existing studies have shown variable effects of increasing temperature on tri-trophic interactions, especially upon the higher trophic levels. This thesis addresses the challenge of understanding how species interactions are affected by temperature by utilising a set of intimately interacting species: galling insects, their host plants and their parasitoid predators. I investigated a set of three co- occuring host plants Solanum inaequilaterum, Rubus moorei and Rubus nebulosus; their galling insects Cecidomyiidae sp. 1 and Dasineura sp. (Diptera); and their guild of nine species of parasitoids. I have quantified the interactions among these three trophic levels along an elevational gradient at five locations within eastern Australian subtropical rainforest. I use a combination of observational and experimental methods to determine the pathways through which temperature affects host plant chemistry, general herbivory, galling insects and their parasitoids.