Fielde's progressive odor hypothesis postulates that certain hereditary nestmate recognition odors in adult ants change progressively with age such that workers will often not accept older siblings that differ from them in age by as little as 40–60 days unless they eclosed among siblings of that age class and learned their recognition cues. Fielde's hypothesis was based on extensive but unsystematic experimental studies which fail to provide unequivocal evidence for this phenomenon. The present study tested this hypothesis for three closely-related ant species, Leptothorax ambiguus, L. curvispinosus, and L. longispinosus, by introducing workers between groups with known age structures and a minimum age difference of eight months. The results invalidate Fielde's hypothesis for these ants. However, progressive odors may yet be found in other species and may be associated with age polyethism.