EFFECTS OF EXPERIMENTAL FORAGER REMOVALS ON DIVISION-OF-LABOR IN THE PRIMITIVELY EUSOCIAL WASP POLISTES INSTABILIS (HYMENOPTERA, VESPIDAE)

Experimental forager removals were performed to assess the mechanisms by which Polistes instabilis colonies regulate their intake of nectar and water. Most foragers gathered nectar, while water was collected by a small number of fixated foragers. Removal of the most active water foragers led to decreases in water foraging, followed by recruitment o f a single replacement water forager. Replacement water foragers were usually recruited from among the workers that had previously collected water at low rates. Water forager removals showed that some workers s pecialized on water collection, but these workers differed in their th resholds of response to colony need for nest cooling. Removal of the m ost active nectar foragers led to longer-lasting (one to three days) d ecreases in colony nectar collection rates, and resulted in replacemen t nectar foragers being recruited away from other foraging tasks or fr om nest tasks. Nectar forager removals were followed by increases in r ates of dominance interactions among nest wasps; this response was not observed after water forager removals. Dominance interactions among w orkers appear to regulate nectar foraging in Ii instabilis. The mechan isms of regulation of foraging differ among materials, and correspond to their maximum rates of collection, predictability of resources, and on the costs of short-term changes in supply to the colony.