Prey recognition by females of the European beewolf and its potential for a sensory trap

Abstract

The asymmetry in mating strategies between males and females may influence the evolution of mate-signalling systems. Exploitation of pre-existing female preferences for certain visual or acoustic stimuli by male courtship signals has been reported from a variety of species. However, information on chemical communication systems is comparatively scarce. The sensory trap model of sexual signalling suggests that female preferences originated from and are maintained by selection pressures in a nonsexual context, e.g. prey recognition. We tested a key prediction from the sensory trap hypothesis for the evolution of the male sex pheromone in a solitary wasp, the European beewolf, Philanthus triangulum . Females hunt exclusively honeybees, Apis mellifera , as provisions for their larvae. Males mark territories with a pheromone to attract females. The co-occurrence of a long-chain alcohol, ( Z )-11-eicosen-1-ol, in the male pheromone and on the cuticle of honeybees suggests that males might exploit a female preference for ( Z )-11-eicosen-1-ol. We used behavioural assays with honeybees and honeybee dummies to investigate whether females use ( Z )-11-eicosen-1-ol for prey recognition. Females used olfactory cues to find and identify honeybees and ( Z )-11-eicosen-1-ol was an essential component of the prey recognition cue. Thus, female European beewolves have a high sensitivity for ( Z )-11-eicosen-1-ol that probably evolved in the context of prey hunting. Therefore, males that included this compound in their sex pheromone probably attracted more females and experienced a selective advantage according to the sensory trap model.