Assessment of pollen stores by foragers in colonies of the honey bee, Apis mellifera L.

Colonies of social insects coordinate many activities in response to changing colony needs. One example is the maintenance of pollen stores in the nest by honey bees (Apis mellifera L.). To adjust pollen intake in an appropriate manner, individual foragers must assess the colony's need for pollen. This assessment could be done either directly, through physical contact with larvae and stored pollen, or indirectly, using information obtained from other bees in the colony. We investigated the mechanisms by which foragers assess their colony's need for pollen. We segregated foragers from non-foragers using either a single screen that permitted contact between the two groups of bees, or a double screen that prevented contact. We supplied the segregated foragers in colonies of both of the screen treatment groups with either a comb containing 300 g pollen {P+) or a comb without pollen (P-). To create a need for pollen in the non-forager compartment of each colony, we provided that compartment with combs bearing 3-5 d old larvae but without any pollen. Foragers on combs with pollen returned 3.5% of the time with pollen, while foragers on combs without pollen returned with pollen 20.7% of the time (P < 0.005). Foragers able to contact their non-foraging nestmates through a single screen {S1) returned with pollen 12.6% of the time, while foragers prevented from contacting nestmates by a double screen (S2) returned with pollen loads 11.7% of the time (P > 0.80). The interaction between the pollen and screen treatments was not significant. These results suggest that foragers adjust their foraging behavior based on their direct assessment of the amount of pollen stored in the colony, and that non-foragers do not provide an excitatory indirect stimulus to foragers.