The influence of pollen quality and pollen-based cues on the nutrition and foraging behaviour of honey bees, Apis mellifera L
Pernal, Stephen F.
Changes in honey bee, 'Apis mellifera' L., worker fitness were determined after feeding caged, newly-emerged bees one of eight pollen diets. Freshly-collected pollen was compared with pollen that had been stored for one year at -30C in an oxygen-reduced atmosphere. Development of hypopharyngeal glands and ovaries was found to be correlated with the amount of protein consumed, and for some diets, protein appeared to be allocated between ovaries and glands differentially. Storing pollen for one year did not affect gland or ovary development. A second experiment was conducted to determine whether honey bee colonies responded to changes in the nutritional quality of their stored pollen reserve. Colony pollen reserves were manipulated either quantitatively or qualitatively, at high and low levels. Foraging rates, and the weight and species composition of pollen loads were determined. Colonies responded to a decrease in the quantity or quality of their pollen reserve by increasing the proportion of pollen foragers, without altering the overall foraging rate. Inexperienced foragers collected heavier loads and more species of pollen per foraging trip, and specialized on larger, more proteinaceous pollen than experienced foragers. Colonies appear to respond to deficiencies in stored protein levels by increasing the gross amount of pollen returned to the colony, rather than by specializing on pollen having a higher protein content. Colony-level responses to deficiencies in stored protein may be manifested by an increase in the ratio of naive to experienced foragers. Foragers receive colony-level feedback about pollen quality in order to match pollen intake with the protein need of the colony. In a third study, pollen-based foraging cues were evaluated using two-choice bioassays in a flight and rearing room. The importance of pollen grain size, protein content, handling time and odour were assessed as foraging cues for worker bees. Pollen odour was the dominant cue foragers used to evaluate pollen, but bees also displayed preferences based upon the size of particles collected. Pollen-seeking behaviours decreased with increases in handling time and foragers did not discriminate on the basis of pollen protein content. Honey bees do not discriminate among food sources based on nutritional quality, but instead, evaluate cues that may affect their efficiency of pollen collection or recruitment to forage sources. Technical details and advances in honey bee flight room design are also discussed.