Being raided by a colony of parasites ought to be a nightmare for a peaceful nest of ants, but in the case of the Sericomyrmex, that's far from reality. Research led from the University of Copenhagen noticed that Sericomyrmex ants were effectively able to use a colony of parasitic invading ants as their own personal group of mercenaries. The parasites' initial presence was certainly harmful — they fed off of the Sericomyrmex's food and young — but, oddly enough, their invasion became necessary for its host's ultimate survival in some circumstances. When yet another type of ant came in to raid the Sericomyrmex's nest, their ongoing parasitic guests wouldn't just turn to fight them, they would flat out destroy them.

Those parasitic mercenary ants, the Megalomyrmex, are able to do that thanks to a potent venom they posses that's far more effective than most ant's biting defenses. That venom also allows them to easily take control of a host colony, but the parasitic Megalomyrmex don't simply use up every resource they can and move on — instead they bind with a host colony permanently, protecting them even as they're harming them. The Copenhagen research team described their findings on Monday in the Proceedings of the National Academy of Sciences. While their results apply specifically to how Sericomyrmex and Megalomyrmex interact, they begin to explore a new complexity to what initially appeared to be a common relationship.