Regulation of worker activity in a primitively eusocial wasp, Ropalidia marginata

Abstract

Ropalidia marginala, a tropical, primitively eusocial, polistine wasp, is unusual in that the queen (the sole egg-layer) is neither the most behaviorally dominant nor the most active individual in the colony. The queen by herself rarely ever initiates interactions toward her nest mates or unloads returning foragers. There are always a few workers in the colony who are more dominant and active than the queen. Absence of the queen from her colony does not affect colony maintenance activities such as foraging or brood care, but it always results in one individual becoming very aggressive and dominant. The dominant worker becomes the next queen if the original queen does not return. The queen does not appear to play any significant role in colony activity regulation. Instead, colony activities appear to be regulated by several mechanisms including dominance behavior toward foragers, feeding of larvae, and the unloading of returning foragers, all mediated by workers themselves. Regulation of colony maintenance appears to be based on direct evaluation of the needs of the colony by the workers themselves. The queen however has perfect reproductive control over all workers; workers never lay eggs in the presence of the queen. It appears therefore that the mechanisms involved in regulation of worker activity and worker reproduction are separate in R marginata. These findings contrast with other primitively eusocial species where the queen acts as a "central pacemaker" and controls both worker activity and worker reproduction.