[betty boop]

I can point out that ants do more or less random exploration and then leave chemical trails when they find something interesting. Other ants follow these trails, stronger scent, more ants.

And this would explain why (seemingly ancient) ant trails have been discovered that run on literally for scores of miles, seemingly connecting many divers colonies. But how do chemical signals account for the way the ants behave in "emergency situations," such as the case where the colony/queen is under attack? Presumably the ants are widely distributed such that scent cues (which require more or less direct or at least close contact) would not be available to direct their behavior. If that is the case, then what does?

[PatrickHenry]

I think it's been demonstrated that insects release "semiochemicals" into the air for rapid communication. Similar chemicals common to other creatures are known as pheromones. (Of course, it could be dryads ...)