Moved from Ants.

The aggressive posturing of these two ants and that one appears to have grabbed onto the palps of the other with her mandibles, plus your comment that they remained 'locked' for a long period, makes me suspect that these are workers from neighbouring colonies who've decided to engage in open hostility rather than simply avoiding one another. Your ID sounds pretty good, too--I also suspect this is one of the fusca group Formica species and very likely the same one as in the 'dragging the fly' portrait...there look to be a lot of similarities between your subjects. My own observations of these types of Formica ants is that the colonies are usually fairly tolerant of one another. Ants from differing nests that happen to meet might not be friendly, exactly, but they don't usually get into tussles either. Once they've 'feelered' each other up and determined that they're strangers, one will more often aggressively lunge at and run the other off, or they'll both bolt in opposite directions, or just carry on and ignore each other. I think the differing responses probably have a lot to do with who's on whose territory at the time and the individuals' own inclinations. And while it's a little hard for me to make out, in that photo in which the third ant is checking the other out, has the checked-out one been grabbed by her antenna? If yes, then I'd say that this is a definite case of territorial intrusion and that the tresspasser's being mauled a bit for her impudence! A nice bit of behaviour caught on camera, whatever's going on. (Only the ants will ever truly know...)

If they were, you would see to winged adults. These are just workers. It is to my understanding that this is how they communicate.