Dorymyrmex bicolor. This species of ant picks up rocks, and drops them on their enemies. Is it war? Define war. Is it tool use? Yes... And what does that say about tool use? What can ants teach us about ourselves?
Bibliography: https://docs.google.com/document/d/1q2kwz6bnI7FqNP1b16qEG1ul_ocKEkrMg8nKm9uqlYI/edit?usp=sharing
