Aphid-Ant Relationships: The Role of Cuticular Hydrocarbons and Different Chemical Stimuli in Triggering Mutualistic Behavior

In ant-aphid interactions, various aphid species offer honeydew to the ant partner and increase their density by ant attendance, whilst others never attend ant species, in which case ants tend to treat them as prey. In this regard, ants should have the ability to distinguish myrmecophile aphid species from non-mutualistic species, so that mutualistic aphids will be accepted as partners rather than prey. Although ant-aphid interactions are now the focus of chemical ecology studies, the role of the different chemical stimuli in determining mutualistic interactions has not been completely clarified. Therefore, we have investigated the cuticular hydrocarbon profile of four myrmecophiles aphid species using GC-MS. We also investigated the behavior of the worker-ants ( Lasius niger L., Hymenoptera: Formicidae) to different chemical stimuli derived from aphids. We applied four treatments and found that the behavior of the ant workers varied depending on the source of the different treatments. In particular, the real aphid Aphis pomi and the sugar solution proved to be the most attractive to the ants, while the presence of pure extract of the individuals is enough to disturb the behavior of the ants. We provide evidence that the key stimuli of the tending behavior could be the CHC patterns of the aphids and the CHC profile of the aphids tends to be genus specific. This research will promote further investigations to test the behavior of ant workers towards other species of aphids and treatment combinations.