For most ant colonies, there’s a straightforward hierarchy: a single queen lays all the eggs, while a caste system of workers manages everything else—foraging for food, nursing baby ants, going to war, and so on. Only males and queens can reproduce, and the rest of the ants are sterile. If the queen dies, the colony usually does, too.

Things are different for the Indian jumping ant, a species with forceps-like jaws and large black eyes that inhabits forests along India’s western coast. In these colonies, if the queens die, workers host bizarre competitions in which the winner becomes the monarch—and capable of producing eggs. The triumphant female ant’s ovaries expand and her brain shrinks up to 25 percent.

But new