Prometheus Bound
I'd just begun my reading of the Greek Tragedians when I did this. The inspiration was the tragedy "Prometheus Bound" by Aeschylus. In that Prometheus is bound to the rock to punish him for stealing fire from the gods and giving it to man. Io comes by, in her form as a cow, tormented by the gadfly, and there is a short exchange between them. That's why the cow and the fly in the lower left corner. Above Prometheus Hermes has arrived to tell him that things will get worse yet. The eagle shows up to start to eat his liver out.