[Dogghound]

Im not sure if its the work of a ichneumon, parasitic wasps such as Aphidius matricariae & Aphidius colemani attack aphids in a different way to this, the egg is laid in the aphid, then it eats the aphids inside body tissue, then it spins a cocoon inside the aphid, the aphid swells and hardens, then it emerges, im unsure as to how this disk would form in this process, although there are several aphid parasites. Some Ichneumons attatch the aphid to the plant, which could possibly be what this is species such as Aphidius eadyi are know for this.