The first photo is an ant milking an aphid for the sweet honeydew. Who needs picnics when you have your own herd of sugar-water cows?
The second photo is two ants talking with their antenna. The ants in this situation seem very on edge, even with each other.
This is the only kind of picture that ever puts me in danger of stings or bites. Ants with their aphids are more aggressive than anything else I photograph. At least the bites and stings aren't dangerous, just a bit painful. What I hate the most is that I'll be clicking away and look down to suddenly discover that I'm under seige by tens of ants.