Does the presence of conspecifics alter defensive behavior of the soybean aphid (Aphis glycines)?

Group defensive behavior is a phenomenon observed in many organisms across taxa, particularly when closely related individuals live near each other as in the case of aphids like the soybean aphid. While some aphid defensive behaviors can benefit both the individual and surrounding aphids, little work has determined whether aphids change their behavior given the presence of conspecifics. In this study soybean aphids were mechanically stimulated to mimic predator attack and elicit defensive behaviors. In response to stimulation, we used video recording to measure whether aphids emitted a cornicle secretion, kicked, waggled, dispersed, or did not react. We were particularly interested in cornicle secretions as they have been linked to alarm pheromones in other aphid species. In this study two treatments were used: aphids alone and aphids in a group. These treatments will allow us to draw conclusions about whether defensive behaviors are altered by the presence of conspecifics, which will be helpful for better understanding the costs and benefits of soybean aphid defensive behaviors and the nature of their intraspecific interactions.