Parasitoid natural enemies have been shown to be highly attracted to chemical cues associated with their preferred host or hosts such as herbivore-induced plant volatiles (HIPVs), cuticular hydrocarbons, or even pheromones. However, parasitoids are often confronted with many cues at once which raises an important question, how do parasitoids discriminate among multiple signals? Past studies have investigated the attraction of natural enemies to host-specific cues before, but few have been paired with behavioral experiments that link parasitoid preference and performance together, especially with tachinid flies. In this study, we tested whether Celatoria setosa, a parasitoid natural enemy of Acalymma vittatum - striped cucumber beetle - could discriminate between complex chemical cues, such as volatiles emitted by plants damaged by A. vittatum (HIVPs) and volatiles emitted by A. vittatum themselves, such as their male-produced aggregation pheromone. To answer this question, we collected headspace volatiles of active A. vittatum damage and measured volatile preference in wild-caught C. setosa female parasitoids using a six-arm olfactometer. We then measured the performances of offspring parasitoids in selected host beetles using both choice and no-choice bioassays. Our results show that parasitoids are attracted to both plants damaged by male and female A. vittatum and that the release of male pheromone increases their susceptibility to parasitism. We also found that parasitoid performance was influenced by host size rather than host sex. Our results further illustrate important parasitoid-host relationships such that behaviors to attract mates can be costly by attracting natural enemies through signal exploitation.
