Host Volatiles Drive Host Preference and Consequently Shape the Fitness of a Generalist Parasitoid Wasp, Meteorus pulchricornis (Hymenoptera: Braconidae).

Host preference is critical to the efficacy of parasitoids in biological control, while the underlying mechanisms remain unclear. Here, we found that the host preference of the generalist parasitoid Meteorus pulchricornis revealed an innate preference for Spodoptera frugiperda, followed by Plodia interpunctella. GC-MS analysis showed distinct volatile organic compound profiles between the two hosts, with 2-hexanol as a shared component. Electroantennogram (EAG) recordings showed that wasp antennae responded more strongly to S. frugiperda than to P. interpunctella odors, suggesting olfaction mediates host preference. Knockdown of the odorant receptor co-receptor, MpulORco, impaired both EAG responses and host preference behavior. Furthermore, wasps reared on S. frugiperda had larger body size and higher fecundity, providing a plausible fitness-based explanation for the observed preference. Collectively, our study reveals olfaction is involved in host preference behavior in a generalist parasitoid and establishes a functional connection between olfactory cues and individual fitness.