Comparative sucrose sensitivity in Apis mellifera and A. cerana foragers

Previous studies in the Western honey bee, Apis mellifera, have shown that pollen foragers have a lower sucrose threshold when tested using a proboscis extension response (PER) assay. Based on the biology of the Eastern honey bee, A. cerana, we hypothesized that A. cerana should have a lower threshold for sucrose. We compared the sucrose thresholds between pollen foragers and nonpollen foragers for A. cerana and A. mellifera in Fujian Province, China. Pollen foragers were more responsive to sucrose than nonpollen foragers in both species. Across the two species, A. mellifera was more sensitive than A. cerana in both types of foragers. In mixed species colonies where both species shared the same colony environment, A. mellifera also showed a higher PER score than A. cerana, so the higher sensitivity of A. mellifera was not due to a different colony environment. Based on these data, we predicted that nectar foragers in A. mellifera should bring in lower concentration nectar compared to that of A. cerana. We determined the nectar concentrations at each hour of seven-paired colonies of the two species of bees for seven days but found that the concentration of nectar foraged A. mellifera was not significantly higher than that of A. cerana.  There might be other mechanisms to enable A. cerana to perform well in areas with sparse nectar resources.