Hello Stubyvast;
I'm sorry I can't help you with aphid ID and I don't know the difference between tending aphids and farming aphids, I thought they were the same thing.
What I can tell you is that the aphid pictured looks like a female. They can produce eggs, but more often they give live birth to "baby" aphids and usually do so quite prolifically, at least on my roses. Any source of sugar substances or honeydew, whether produced by plants, aphids, scale insects, or coccids, can be a source of food for ants. Ants encourage the aphids to expel honeydew by stroking them with their antennae and they'll also move them to more desirable places on a plant, usually fresh, new growth. Perhaps this is where the farming analogy comes from. They milk the aphids and move them to better pastures. They also protect them from predators like lady bugs and lacewings. Ants have also been seen to eat unwanted aphids, ones that are old or dying and males.
Your aphid appears to be taking sap from the plant; therefore, it should produce honeydew. I'm sure it would make a suitable cow in your ant's herd.
RPT
My father always said I had ants in my pants.