Describing ant colonies as entities with a personality instantly reminded me of the dialogues between the anteater and the ant hill in Godel Escher Bach.
In it, Hofstadter likens an ant colony to the human brain, and ants to neurons in an attempt to explain how intelligence appears to be an emergent quality.
This shouldn't really be a surprise to anyone at this point. Environmental and inter-species signalling? Why would neurons communicating with each other in the presence of external signalling inputs be any different, fundamentally, than ants (with brains and neurons of their own, but not as many) communicating with each other in the presence of external [environmental] signalling inputs? There are scale differences but that's it. Aggressiveness or passivity is not something you'd only expect to emerge from highly complex biological signalling networks. If you can make people more peaceful by putting them in drunk tank pink rooms, it's perfectly plausible that you could find some things that make ant colonies more aggressive, and some things that make them less aggressive.