Predatory hoverflies select their oviposition site according to aphid host plant and aphid species

The hoverfly Episyrphus balteatus De Geer (Diptera: Syrphidae) is an abundant and efficient aphid-specific predator. Several aphidophagous parasitoids and predators are known to respond positively to aphid-infested plants. Semiochemicals from the latter association usually mediate predator/parasitoid foraging behavior toward sites appropriate for offspring fitness. In this study, we investigated the effect of aphid host plant and aphid species on foraging and oviposition behavior of E. balteatus. Behavioral observations were conducted using the Noldus Observer v. 5.0, which allows observed insect behavior to be subdivided into different stages. Additionally, the influence of aphid species and aphid host plant on offspring fitness was tested in a second set of experiments. Acyrthosiphon pisum Harris and Megoura viciae Buckton were equally attractive for E. balteatus whereas Aphis fabae Scopoli (all Homoptera: Aphididae) were less attractive. These results were correlated with (i) the number of eggs laid, which was significantly higher for the two first aphid species, and (ii) the fitness of hoverfly larvae, pupae, and adults. Two solanaceous plant species, Solanum nigrum L. and Solanum tuberosum L. (Solanaceae), which were infested with Myzus persicae Sulzer (Homoptera: Aphididae), were also compared using the same approach. Discrimination between these two M. persicae host plants was observed, with S. tuberosum being preferred as an oviposition site by the predatory hoverfly. Larval and adult fitness was correlated with the behavioral observations. Our results demonstrated the importance of the prey-host plant association on the choice of the oviposition site by an aphid predator, which is here shown to be related to offspring fitness.