AN EXPERIMENTAL-STUDY OF THE EFFECT OF COLONY RESOURCE LEVEL MANIPULATION ON FORAGING FOR POLLEN BY WORKER BUMBLE BEES (HYMENOPTERA, APIDAE)

Two free-foraging colonies of Bombus terricola Kirby were stressed, on alternate days, by removing either their honey or their pollen stores . The amount of pollen taken into the colonies by foragers was signifi cantly greater under pollen stress than under honey stress. This effec t was not due to an increase in the number of foraging trips but rathe r to an elevated rate of pollen acquisition per foraging trip.