(...movie is loading, it will play when download is finished, if you have a fast Internet connection it should take < 1 min.)

Army ants hold off the leafcutters
(18 seconds,9.2 Mb)

Leafcutter ants form long, very busy trails that can reach for hundreds of meters through the forest. Because leafcutters are so common, army ant swarms often cross trails and block them. It is quite amusing to watch the traffic build up on the leafcutter trail as thousands of army ants stream by. The leafcutters, leaves held overhead, walk frantically back and forth trying to figure out how to get past. Often there is a stick or piece of grass near by that bridges the army ant trail. The leafcutters cross over it like a freeway bridge and continue on their way.
In this clip, the army ants form a tight line, blocking the leafcutters and protecting the foraging column from them. I saw a lot of these interactions but the ants almost never fought. Army ants and leafcutters are both very vicious ants - a battle between them would quickly lead to the death of both ants. Instead they sparred and muscled up to each other, bumping antennae and mandibles and looking fierce, but never actually attacking.