Aspects of worker reproduction in four social wasp species (Insecta: Hymenoptera: Vespidae)

The question of male production by workers in social wasp colonies (Vespinae) has long concerned researchers. Its occurrence would suggest that queen control of colony reproduction is not absolute and that the evolution and maintenance of eusociality in vespines may have been promoted through direct reproductive ability of the worker caste. Dissections of over 3,300 workers from 34 Paravespula and Vespula colonies failed to reveal a significant contribution to male production by workers in most colonies. In those colonies which did contain ovary-developed workers, the wasps tended to be larger than their nestmates in two of the species. On the other hand, ovary-developed workers could not be characterized as specializing in intra- or extranidal tasks in any species. The onset of worker ovarian development was associated with increased size of nests and occurred predominantly in late-season colonies. The near-complete sterility of workers through most of the season suggests that models invoking mutualism and characterizing workers as 'hopeful reproductives' cannot explain the maintenance of eusociality in vespine wasps.