A member of the non-reproductive laboring caste in semi-social and eusocial species.

The existence of a worker caste presupposes the existence also of royal (reproductive) castes. In termites, the term is used in a more restricted sense to designate individuals in the family Termitidae that completely lack wings and have reduced pterothorax, eyes, and genital apparatus.

A member of the subcaste of the largest workers; especially, in ants.

With ants, the subcaste is usually specialized for defense; so, that an adult belonging to it is often also referred to as a "soldier".

In polymorphic ant series involving three or more worker subcastes, an individual belonging to the medium-sized subcaste or subcastes.

A member of the smallest worker subcaste; especially, in ants.

The dwarf workers produced from either the first ant broods or later ant broods that have been subjected to starvation.

Nanitic workers occur in both monomorphic and polymorplhic species.