Learning in herbivorous insects: dispersing aphids spend less time evaluating familiar than novel non-host plant species.

For many organisms, dispersal may be a high-risk activity, and dispersers are likely to have behavioral, physiological, or other adaptations that increase the probability they will successfully settle in new habitat. Dispersing aphids, for example, are small-bodied, relatively weak flyers that must navigate through a complex landscape where non-host species may be much more common than suitable hosts are. While previous research has focused on how dispersing aphids locate and evaluate host species, little is known about how they interact with the non-host species they encounter while host searching. Here, I report on an experiment to test the hypothesis that dispersers of Aphis fabae spend less time evaluating non-host species with which they have had prior experience than novel non-host species. Aphids consistently spent less time in contact with familiar non-host species than novel non-host species, but the magnitude of this effect varied for different non-host species. Aphids that had previously encountered rose spent less time interacting with rose than with raspberry or goldenrod, and aphids that had previously encountered raspberry spent less time interacting with raspberry than with goldenrod. Aphids that had previously encountered goldenrod showed a less pronounced and statistically non-significant reduction in time spent interacting with goldenrod relative to either raspberry or rose. The ability to recognize previously encountered non-hosts may allow aphids to navigate more efficiently through an environment in which they face many more non-hosts than hosts, and therefore increase the probability that a disperser will ultimately locate and settle on an appropriate host plant.