The order Hymenoptera is one of, if not the most, species-rich order of animals, primarily driven by the many parasitoid wasps and their unique arthropod hosts. As hosts are necessary for survival, host location and selection have direct fitness implications. Semiochemicals, also known as infochemicals, from either the host herbivore or the plant are just one of many cues that parasitoid wasps use to locate a suitable host. The reliability-detectability hypothesis suggests that infochemicals from the host herbivore are the most reliable indicators of host presence. However, as localized signals, infochemicals are less detectable by parasitoids. Alternatively, infochemicals from plants are detectible over longer distances, although these signals are less reliable indicators of host herbivore presence. In this study, we explore the occurrence of infochemicals emitted by plants and their association with parasitoid host selection. We identified 112 phytochemical compounds extracted from Eucalyptus leaves that had been attacked by leaf beetle herbivores (Chrysomelidae) which had in turn been parasitized by Eadya larval-parasitoid wasps (Braconidae). Using several phylogenetic and statistical approaches, we conclude that host selection in two species of Eadya wasps is heavily influenced by infochemicals from the plant 1st trophic level. With this evidence, we propose amending the reliability-detectability hypothesis to include direct interaction between the 1st and 3rd trophic levels in a scenario where an oligophagous parasitoid utilizes oligophagous hosts.