The main differences between aphid species that are “tended” (farmed) by ants include longer mouthparts, shorter cornicles, and winglessness. These adaptations are probably more strongly related to the fact that protection from the ants means they don’t need “predator avoidance traits” anymore than having anything to do with the quantity or quality of the honeydew the aphids produce. But the main advantage ants offer to aphids is that they reduce competition for the aphids by getting rid of the “untended” aphids from an area. Source: [mooneyGeneticallyBasedPopulation2011](https://doi.org/10.1007/s11829-010-9110-7)