LACK OF EXPERIMENTAL-EVIDENCE FOR PHEROMONAL INHIBITION OF REPRODUCTION AMONG QUEENS IN THE ANT LEPTOTHORAX-ACERVORUM

This paper describes an experimental test of the hypothesis that queens in multiple-queen (polygynous) societies of ants inhibit the reproduction of nestmate queens with pheromones. Three colonies of the facultatively polygynous ant Leptothorax acervorum with marked queens were each observed for 75 h, in three phases of 25 separate, hour-long bouts per phase, over 4-8 weeks in total. In each colony, all queens were present for the first phase; for the second phase, queens were removed so that only the queen initially laying least eggs (the focal queen) was present; and all queens were again present for the last phase. The pheromonal inhibition hypothesis predicts that in each colony the fecundity (egg production) of the focal queen should have risen in the second phase and fallen in the third phase. However, although the focal queen's fecundity did rise in phase 2 in each colony, these rises were small and were maintained in phase 3 in two out of three colonies, suggesting that the initial increase was not due to the experimental treatment. In addition, the focal queens' rates of egg eating, feeding from workers and larvae, grooming, receiving grooming and handling brood either did not change with the experimental treatment or changed in different directions across the three colonies. Therefore this experiment found no firm evidence among L. acervorum queens either for strong, short-term pheromonal inhibition of reproduction or for inhibitory effects of queens on other queens' behaviour. © 1993 The Association for the Study of Animal Behaviour. All rights reserved.