Photo: ZombyLuvr (flickr)
A species of insect is eusocial if it meets these main criteria. Many adults, including various generations of them, live together as a colony. They cooperate in building the nest and caring for the young. And there is some form of a reproductive hierarchy. Often this means there is a single queen who births all of the colony’s offspring. Bees, ants, wasps and termites are all examples of eusocial critters.
For the longest time scientists thought that only species of insects could be eusocial, but there’s actually a mammal that also qualifies? This mammal is the naked mole rat — a small rodent native to East Africa.
Another requirement for being considered eusocial is that there should be some permanent physical trait that distinguishes castes of the colony from one another. For instance, in the ant world, the queen has wings, but the worker ants do not.
In the case of the mole rat, the queen has specialized vertebrae that make her body longer than her cohorts. The extra length allows her to fit through the narrow tunnels of the home despite carrying up to twenty-seven fetuses at a time.