Continuing to explore the intriguing world of the Indian paperwasp Ropalidia marginata, here we will focus on their fighting behaviour. When wasps fight, there is, as expected, a winner and a loser. The winner is said to have shown dominance behaviour, and the loser is said to have shown subordinate behaviour. What is the function of such dominance subordinate behaviour? We saw in the 7th article in this series [1] that in the context of founding new nests, wasps fight to decide who would be the queen and who would be the worker. We then saw in the 8th article in this series [2] thatwhen wasps have to decide who would be their next queenin a mature colony, they do not decide by fighting, although they fight for other reasons. We will see in this article that workers continue to show dominance-subordinate behaviour in mature colonies. What is the function of this aggression displayed by the workers? In this article, I will describe two simple experiments that help us answer this question, and show that the function of wasp aggression can be quite different in different contexts.