I have no idea what's going on here. At first glance I thought maybe I as looking at some variety of "aphid-farming" ants. But, on closer inspection, those little green nodules on the plant don't appear to be aphids. I'm not sure what they are. There were also quite a few tiny flies (gnats?) walking up and down the stem of the plant. I'm not sure if they had anything to do with the ants/nodules or not, but there were quite a few of them in close proximity, often coming into direct contact with the ants. Although they didn't seem to interact at all, just walking past/over each other.