The effect of queen number on nestmate discrimination in the facultatively polygynous ant Pseudomyrmex pallidus (Hymenoptera: Formicidae)

We present evidence indicating that the level of nestmate discrimination in the facultatively polygynous ant Pseudomyrmex pallidus varies predictably with the number of queens in the colony. P. pallidus workers were introduced into observation arenas in either nestmate or non-nestmate pairs. During the 5-min period immediately following the first contact between test ants, all interactions and relative distances were recorded. Aggression between non-nestmates was negatively correlated with the number of queens in the colony and distance between nestmates was positively correlated. These results are consistent with predictions of Reeve's (1989) optimal acceptance threshold model.