Opposites attract…or do they? Examining the influence of Acalymma vittatum in the host-plant finding decisions of Anasa tristis

The attraction of an insect herbivore to the pheromone cues of a closely related herbivore species can occur but is rare between distantly related herbivores of different feeding guilds. Optimal foraging theory predicts that an attraction to a co-occurring herbivore that shares resources and habitats could indicate a fitness benefit from it. The attraction of the squash bug (Anasa tristis, Coreidae) to the aggregation pheromone, vittatalactone, and associated cues of the striped cucumber beetle (Acalymma vittatum, Chrysomelidae) is an example of this uncommon attraction. How An. tristis prioritizes cues when encountering a host plant damaged by Ac. vittatum is unknown. This study sought to examine what cues are prioritized by An. tristis, and if attractive cues from Ac. vittatum could lead An. tristis to a less preferred host. Through a series of binary choice assays, it was found that An. tristis is selective in its host plant choice. In these experiments, An. tristis preferred both undamaged and Ac. vittatum damaged summer squash (Cucurbita pepo), a known host plant, with no preference for C. pepo plants baited with vittatalactone or cucumber (Cucumis sativus) plants damaged by A. vittatum. While vittatalactone was not the driving force in these small-scale choice assays, previous research has shown the attraction of An. tristis to vittatalactone at a larger field scale. These results combined suggest that cues from Ac. vittatum, such as vittatalactone and herbivory, could be considered in the initial host-plant location, however, An. tristis prioritizes accepting a suitable host-plant variety over those cues.