At least one of the more than 12,000 species of ants is selfless and heroic in battle.
Megaponera analis, a species found in sub-Saharan Africa, hunts in groups for termites. A scout goes out to reconnoiter a termite nest, then returns to lead a battalion of 200 to 500 ants to the buffet.
Larger ants break open the nest; smaller ants follow, rushing in to grab the prey. But soldier termites with hard heads and big jaws fight them off, and the injury rate is high among the invaders.
So the ants rescue their injured buddies, carrying them back to the nest where they can recover to fight again.
In an experiment described in Science Advances, Erik Thomas Frank and his colleagues at the University of Würzburg in Germany forced injured ants, or ants with termites still clinging to them, to try to return to the ant colony without help.
Almost a third died, mostly eaten by lurking spiders.
But when injured ants had help getting home, the casualty rate . Using a mathematical model, the researchers calculate that this unusual caregiving behavior allows the ants to maintain a colony size 28.7 percent larger than they otherwise could.