Peace breaks out (among ants)

Given that different ant species, and different colonies of the same species, are usually extremely hostile towards one another - fighting, slave making, that sort of thing - this report of a small species living peacefully, and perhaps symbiotically, in the nest of a large one is Quite Interesting. The ants live in hollow tree branches in West Africa; the small one (Pyramica maynei) is also capable of living on its own, but might benefit from the secure environment of the large species' (Platythyrea conradti) nest, possibly in exchange for keeping the place clean.