Something happening all over the country right are territorial battles by ants. In this case Tetramorium caespitum, The Pavement Ant. Most ants actually get along fairly well with one another. I've actually found this species nesting happily between Lasius claviger and Camponotus castaneus. See here. But when it comes to other colonies of T. caespitum they declair war!
The two colonies send as many workers as they can and a big mass of ants meets in the middle. Despite so many ants involved there seems to be relatively few casualties. For the most part a lot of the ants bump heads and scurry around the mob. A certain few however are ganged up on and torn limb from limb.
Usually the weaker colony isn't destroyed unless it's significantly smaller. The victorious colony gains more territory for their workers to scavenge for food. Despite the fact that other species of ants, sometimes much larger colonies, are nesting in that territory.
Unfortunately I've never been able to devote a lot of time to observing this sort of thing. I'd love to see two colonies going at it and monitor them over the course of the day. One observation I've noticed was these wars only seem to happen during the day. Perhaps they're just harder to find at night?