What species of aphid do ants farm?

[Deleted]

I know that some ants like Lasius niger farm aphids, but what species of aphid do they farm or can it be any species. 

[TenebrousNova]

I've definitely seen them farming the common black aphids. Beyond this, I'm not sure.

[Wood~Ant]

Blackfly or Greenfly aphids are the most common found on a lot of garden plants. Ants will farm these, and Lasius flavus farm root aphids which tend to be either white or a pale caramel colour.
Wood Ants go for almost any of the sap sucking insect they find on trees or bushes, so whatever colour of aphid species you may find on garden plants such as rose bushes or the soft growing tips of flowering plants, including weeds, can be farmed for honeydew by ants. Aphids and Ant Farmers