What Is Eusociality?

Eusociality is the highest level of social organization in animals. It is defined by several key characteristics:

• Division of labor into reproductive and non-reproductive castes, such as queens (reproductive), workers, and soldiers (non-reproductive).

• Cooperative care of offspring, including care for young that are not one’s own.

• Overlapping generations within a colony, so that multiple generations live and work together.

• Specialized behavioral groups, or castes, that perform distinct roles essential for the colony’s survival.

Eusociality in Ants and Bees

In eusocial insects like ants and bees:

• The queen is the primary reproductive individual, laying eggs to produce the next generation.

• Sterile female workers perform tasks such as foraging, brood care, nest maintenance, and defense.

• Soldier drones (in ants) or drones (in bees) may have specialized roles, such as colony defense or mating with queens.

This division of labor is so pronounced that members of different castes often develop distinct physical and behavioral traits, optimized for their roles.

Why Is This Not Sub-social, Group Selection, or Just Altruism?

• Sub-social refers to species where parents care for their own young but do not form complex, multi-generational colonies with reproductive division of labor.

• Group selection is a theoretical concept about evolution favoring traits that benefit the group, but it does not specifically describe the structural organization seen in ants and bees.

• Altruism is a behavior, not a social structure; while altruism is common in eusocial societies, the defining feature is the caste system and cooperative brood care.

The Ultimate Example

Eusociality is most widespread in the Hymenoptera order (ants, bees, and wasps), making these insects the textbook example of this social system. The presence of queens, sterile workers, and soldiers working together for the colony’s success is the hallmark of eusociality.

Correct answer: (1) Eusociality