Queen Pheromone and Monopoly of Reproduction by the Queen in the Social Wasp <I>Ropalidia Marginata</I>

Abstract

Ropalidia marginata is a primitively eusocial (truly social) wasp found in peninsular India. It is different from the typical primitively eusocial species in having docile queens that cannot use aggression to maintain reproductive monopoly. Recent studies using chemical analysis and bioassays indicate that Dufour’s gland is a source of the queen pheromone in this species. Queens appear to signal their presence to workers through their Dufour’s gland compounds, possibly by applying them on the nest surface, and this results in suppression of reproduction by workers, resulting in reproductive monopoly by the queen. The Dufour’s gland was found to contain saturated long chain hydrocarbons, which have recently been suggested to be the ancestral state of fertility signals in Hymenoptera. The Dufour’s gland composition differed significantly between queens and workers, and was also correlated with the state of ovarian development, varying continuously as a function of ovarian development, thereby advocating the honesty of the queen pheromone. This elucidates the mechanism of maintenance of eusociality through pheromonal queen signalling by the Dufour’s gland compounds.