Eusociality

Eusociality is a form of social organization usually defined by three features: adults of more than one generation live together in a colony, they cooperate in caring for the young, and labor is divided between reproductive individuals and workers that breed little or not at all. A honeybee hive is a typical example: one queen lays the eggs while thousands of her daughters gather food, build comb, rear larvae and defend the nest.

Eusociality has evolved relatively rarely, but where it has, it has been very successful. It occurs in all ants and termites and in some bees and wasps, and also in a few aphids, thrips, beetles and snapping shrimp and in two mammals, the naked mole-rat and the Damaraland mole-rat. It puzzled Darwin: how could natural selection favor sterile workers that leave no offspring? The most widely accepted answer is kin selection. Workers usually help raise their own siblings, who share many of their genes, so helping their mother breed can pass on more copies of those genes than breeding alone would. Some biologists argue that ecological pressures, such as defending a valuable nest, matter more, and the debate continues.

In many species, pheromones help maintain the division of labor and coordinate the colony.