Differences in inhibitory capability among queens of the ant Solenopsis invicta

The abilities of various categories of queens of the fire ant, Solenopsis invicta Buren, to inhibit de‐alation by virgin queens are compared by means of a standardized bioassay that detects the presence of an inhibitory pheromone. Highly fecund (high weight) queens of monogynous colonies and virgin replacement queens in queenless colonies have a significantly greater inhibitory capability than queens of lower fecundity (lower weight). In polygynous colonies, inhibitory effectiveness is also positively related to the fertility of individual queens, although no pheromone can be detected in queens that lay few eggs. Alate virgin queens that have overwintered in the parental nest, and sexually mature spring‐reared virgin queens, either do not produce the pheromone, or produce too little to be detected. These results are discussed in relation to the degree of ovarian development of different queen categories and in relation to the social status of these queens.