Experimental male size manipulation in Polistes dominula paper wasps: to be of the right size.

In previous studies on Polistes dominula paper wasps, male size affects both mating success and territorial strategy. Larger males occupy exclusive territories at leks, i.e. landmarks where they achieve most copulations (Residents), while smaller males search for females in sub-optimal locations across territories as Transients. We here observed spatial and mating behaviour of a selected size-bimodal population of males, caught at leks and released in semi-natural conditions. Residents, mainly Large males, were more successful in sexual interactions with virgin females than Transients. Residents also engaged in “mate guarding”, reported here for the first time. On the other hand, some Small males achieved copulations inside their own territories, at foraging sites or by grasping females and falling on the ground. Both tactics of mate access – patrolling a territory for perched females or intercepting females – were successful, the former more than the latter, whereas size itself was irrelevant on sexual performance and mating success, regardless of our size-bimodal sample. Moreover, we carried on morphological analysis of male reproductive apparatus. Males with larger accessory glands, directly involved in reproductive success in many insects, mated more than males with smaller accessory glands, regardless of male body size.