Regulation of host colony activity by the social parasite Polistes semenowi

The productivity of social groups depends critically on effective regulation of work effort among group members. In social insect colonies, regulation of work may be decentralised or alternatively may be controlled by one or a few individuals (‘pacemakers’) within the colony. Social parasites, which usurp host colonies and replace the dominant as the principal reproductive, similarly depend on efficient regulation of work by hosts to rear parasite offspring, but few studies have explored the strategies used by parasites to achieve this. We compared the role of the social parasite Polistes semenowi in regulating host activity with that of the dominant individual on unparasitized nests of the host species, P. dominula. Dominant foundresses acted as pacemakers within unparasitized colonies, interacting frequently with colony members to initiate activity bursts and foraging trips, whereas parasites did not initiate more activity than the average colony member. Nonetheless, overall activity levels were similar in parasitized and unparasitized colonies, indicating that parasites may use other, indirect means to control the host activity. Colony activity did not change significantly following the removal of parasites or dominant host foundresses, perhaps because other individuals rapidly assumed the dominant position, or because of persistent indirect effects on colony activity. The role of P. semenowi in regulating the host activity differs strikingly from that reported for a second Polistes social parasite, P. atrimandibularis, suggesting that different Polistes social parasites may have fundamentally different social roles within host colonies, despite being closely phylogenetically related to one another.