Slave-making ants, as their name implies, excel at kidnapping enemy species' babies and turning them into mindless automatron workers. Most slave-making ants live in the tropics, but one "tribe" of these creatures lives in the U.S. From that tribe, researchers knew of two species already. Now, they've found one more to add to the list, Temnothorax pilagens, named for the Latin word pilere, "to plunder" or "to pillage," the researchers explain in a release.

Specimens belogning to T. plagens were plucked up from Michigan and Ohio, but the ant lives throughout the Midwest and in eastern states. The tiny pillage ants, which grow to be just 2.5 millimeters long, use stealth to snatch up their enemies' babies. Enemy ant species live in hollowed out acorn "fortresses," which contian just one small hole as the entrance and exit. To maximize secrecy, the pillage ants limit operations to just four individuals, which sneak in the front door of the acorn and begin stealing larvae, eggs and, sometimes, even adults. The pillage ants evade detection by using a chemical mask that prevents their enemies from sniffing them out. Oftentimes, the victimized ants don't even react to the intrusion.

On occasion, however, the victim ants do notice that their young are being stolen. However, the researchers write, "the chance of a slave ant to win a fight with a pilage ant is nearly zero." The pillage ants wield their stingers in an impressive display of "artistic rapier fencing," stabbing attackers at a squishy spot in their necks. Their victims are paralyzed and frequently die.

The pillage ants are benevolent enslavers, however. It does them good to allow their victim species to continue living under the guise of safety in thier acorn nest—even after a raid. That way, when the pillage ants need more baby slaves, they can simply come knocking on that nut door and collect their new dues.