Videotaped observations (371.3 h) were conducted in 1995, 1996, and 1997 on 50 multiple-foundress colonies of the social wasp Polistes fuscatus. Observations were made during the mid-preworker, late-preworker, and early-postworker stages of the colony cycle. The vast majority of lost subordinate cofoundresses (62 of 77) disappeared during the time interval from 2 weeks before to 4 weeks after the emergence of the first workers. The loss of subordinates did not appear to be the result of senescence or foraging-related mortality. Lost subordinates were from productive and presumably healthy colonies. In colonies containing two or more subordinates, lost subordinates had significantly greater dominance ranks than expected. There was no behavioural evidence that lost subordinates were evicted from their colony by queens, other subordinate foundresses, or workers. Lost subordinates were not observed to renest, join sister colonies, or adopt orphaned nests. Our results indicate that lost subordinates leave colonies of their own volition. Indirect evidence from other studies suggests that subordinates may disperse and usurp colonies from other sites.