Worker age, size and social status in queenless colonies of the ant Leptothorax gredleri

Workers in queenless colonies of the ant Leptothorax gredleri form dominance hierarchies by antennation bouts and biting. The frequency of aggressive interactions peaked when the ants became active again after hibernation, a second time in summer, when new workers eclosed from overwintered brood, and a third time when we experimentally removed the queen. High-ranking individuals were more active and had greater ovarian development than their low-ranking nestmates. We investigated what proximately determines a worker's social status. Neither age, previously shown to affect hierarchy rank in several other social insects, nor levels of fluctuating asymmetry appeared to be important in worker rank orders in L. gredleri. High-ranking workers were on average larger than low-ranking individuals and body size and rank were correlated in four of five colonies investigated. However, individuals of similar age but different social status did not differ in size. Copyright 1999 The Association for the Study of Animal Behaviour.