Ants farming blackfly on the wisteria shoots

I noticed that the wisteria growing up the side of the cabin in the garden has very few flowers this year. Last year they were profuse.

When I looked more carefully at one of the new shoots I saw a telltale dark mass of blackfly on a couple of the shoots. I got up close and then noticed quite a few ants moving very rapidly around the blackfly. Then I remembered that ants marshal blackfly as if they were farming them, so that they can profit from the sugars released when the blackfly bite into the soft tissue of the plant's stem. The ants protect the aphids, and then lick honeydew off their bodies.  

A little bit of googling brought up this:
Ants are often a precursor to an aphid attack because they farm them in what is known as a mutualisitic relationship. Ants milk the aphids for a sugary secretion called honeydew and in return they protect them from predators and move them on to promising pastures. The scout ants on the new runner will soon plant more blackfly near the growing tips to extend the colony