When I've messed with an ant and return her frustrated and scared from being trapped to her colony her presence causes a visible disturbance.
She must smell of things that don't belong. If she is upset, her sisters grow upset too. It spreads like a ripple, but if it's just one ant as she calms it's forgotten.
But, if too many ants in one area are alarmed like that the whole colony may start to "boil."
Everyone knows what "boiling ants" looks like, but I think I should break it down.