Yesterday I was walking around in a park in Fortaleza, Brazil, and saw some strange nests which I at first thought belonged to termites, or maybe wasps. As I got closer, I discovered they were inhabited by ants.
I took pictures of this little one, since it was around eye level, but some were huge - as big as basketballs - but these were much higher up on the trees.
The ants were reddish brown, apparently monomorphic, and very fast and active, never standing still. I couldn't focus on them at all, at least no with my old phone camera. This one is the best I got.
These ants were very aggressive and didn't like me being near the nest (I think I accidentally stepped on some when getting close to the tree, so I can't blame them...). They quickly ran up my legs and got under my clothing, nipping me, but luckily they didn't sting.
I'm pretty sure these are dolichoderines, and reading about the ones found near me, the genus Azteca seemed the only one to fit. Wonder if anyone has kept them? Would be nice if they build these intricate structures in captivity, but they were so quick and fierce I'm not sure I would be up to the task!