eusociality

thumb|upright=1.5|Co-operative brood rearing, seen here in honeybees, is a condition of eusociality.

Eusociality (Greek 'good' or 'true' and social) is the highest level of organization of sociality. It is defined by the following characteristics: cooperative brood care (including care of offspring from other individuals), overlapping generations within a colony of adults, and a division of labor into reproductive and non-reproductive groups. The division of labor creates specialized behavioral groups within an animal society, sometimes called castes. Eusociality is distinguished from all other social systems because individuals of at least one caste usually lose the ability to perform behaviors characteristic of individuals in another caste. (Narrow definitions, such as that of Crespi & Yagena, require that an irreversibly sterile caste be present, but this is not universally agreed on.) Eusocial colonies can be viewed as superorganisms.