In social insect colonies the sterile individuals that assume the worker role realize their reproductive potential through working and rearing the queen's brood. We have examined the role of the presence of brood in the nest as a determinant of caste in the social wasp Polistes exclamans Viereck. We predicted that wasps in colonies where there was no brood would behave like future queens, while wasps in colonies in which brood care was an option would behave like workers. Brood presence was manipulated by removing eggs and larvae or the whole nest from experimental colonies and leaving brood in control colonies. Ability to tolerate cold temperatures was used as an indicator of caste when comparing females emerging in experimental colonies to females emerging in control colonies. Females emerging in experimental colonies survived longer at cold temperatures than those emerging in control colonies. This indicates that females developed characteristics more typical of future queens in response to deprivation of brood. P. exclamans is characterized by small colonies whose nests are destroyed frequently. Therefore caste plasticity in adult females of P. exclamans is advantageous.