Applied to the condition or to the group possessing it in which individuals display all of the following traits: cooperation in caring for the young; reproductive division of labour with more or less sterile individuals working on behalf of individuals engaged in reproduction; overlap of at least two generations of life stages capable of contributing to colony labour (Wilson, 1972); compare subsocial.

Term applied to insects, such as termites, ants, and many bees and wasps, in which individuals cooperate in the care of offspring, there are sterile castes, and generations overlap.

Eusociality is the phenomenon of reproductive specialisation found in some species of animal, whereby a specialised caste carries out reproduction in a colony of non-reproductive animals........