DEFINITION: Eusocial (of ants)
Eusocial means truly social. Applied to the condition, or to the group possessing it, in which individuals display all of the following three traits:
1) cooperation in caring for the young;
2) reproductive division of labor, with more of less sterile individuals working on behalf of reproductive individuals;
3) and overlap of at least two generations of life stages capable of contributing to colony labor.
From the Glossary of “The Ants” by E.O. Wilson & Bert Hölldobler
