Species- and context-dependent responses of green lacewings suggest a complex ecological role for methyl salicylate (Neuroptera: Chrysopidae)

Herbivore-induced plant volatiles (HIPVs) are important semiochemicals in multitrophic plant-insect interactions, attracting natural enemies of phytophagous insects. Numerous studies have reported attraction of natural enemies to the HIPV methyl salicylate, including green lacewings. However, previous reports provide conflicting data, as some studies report significant attraction, whereas others found moderate or no attraction, even for the same taxa. In the current study, we conducted field experiments in Hungary with methyl salicylate and known attractants for Chrysoperla spp. and Chrysopa spp. lacewings. Both males and females of Chrysoperla carnea species complex were attracted to methyl salicylate, but to a much lesser extent compared to phenylacetaldehyde, a previously known floral attractant. When presented in combination, methyl salicylate showed a synergistic effect, confirming results of previous research performed in Hungary. On the other hand, methyl salicylate did not attract Chrysopa formosa. When tested in combination with known sex attractants for C. formosa males, it synergized male attraction to the aphid sex pheromone component (1R,4aS,7S,7aR)-nepetalactol; however, in combination with squalene, no synergistic effect was found. The results suggest that the responses of green lacewings to methyl salicylate are context-dependent, and the ecological role of the compound may be more complex than previously expected.