An insect society, such as an ant colony, represents a critical test case for general theories of evolution, as Darwin himself recognized. Ant workers are sterile, and in general their sole means of reproduction resides with their mother queen. A fairly common yet unstudied characteristic of ants is that a colony can split up into several discrete nesting units, a process called polydomy. When this happens, workers in colony subunits without the queen are released from her influence, and can proceed to behave in ways to maximize their own fitness. Thus studying polydomy, the process of colony fractionation, is important to a full understanding of social evolution. Polydomy is best studied by applying hierarchical selection models. In these formulations, evolution proceeds on several levels: the entire colony; different nesting units that comprise the colony; and individual workers and queens within those nesting units represent levels in the selection hierarchy. Dr. Herbers will study the process of colony fractionation among primitive ant species in Australia, where polydomy is just now beginning to evolve. A combination of field studies, laboratory aggression assays between members of different nests, and biochemical analysis will allow her to determine when and how often colonies split up. Furthermore, measuring the fitness of all individuals within nests will provide insight into the nature of selection at each level in the hierarchy. This is a proposal for a Career Advancement Award under the aegis of the Research Opportunities for Women. It is likely to result in a significant enhancement of the scientific field as well as Dr. Herbers' own career.