Do aphid soldiers sequester secondary plant compounds to combat natural enemies?

Many social insect species have evolved specialized means of defense, including some aphid species. First-instar nymphs of the social aphid, Pemphigus obesinymphae (P. obes), an aphid that forms galls on the petioles of poplars, do not have special morphological features, but still act as ‘soldiers’ to defend their maternal group from predators. Here, we first demonstrate that P. obes soldiers exhibit effective defense by attacking and killing other insects much larger than themselves. A closely-related non-social species, Pemphigus populi-caulis, does not exhibit comparable defense. This suggests that closely-related species differ substantially in the ability to deter predators. Secondly, we investigate a possible mechanism for aphid defense: whether soldiers sequester and utilize secondary plant compounds as types of ‘venoms’.