These ants have quite effectively corralled their herd of honeydew producing treehoppers.
There’s a lot to see here if you look carefully. First, it looks like quite a few of the life stages of the treehoppers are present. There’s the dark adult in the center, an early instar in the bottom center, and the majority appear to be middle instars.
In the detail below, you can see the ant on the right has just taken a drop of honeydew and the dark adult has a drop waiting.