Combined gas chromatography-electroantennogram characterization of alfalfa floral volatiles recognized by honey bees (Hymenoptera: Apidae)

This study was designed to investigate antennal response of honey bees, Apis mellifera L., to alfalfa floral volatiles and to assess among- and within-hive variation in average antennal response to these compounds. Ten of the principal (Medicago sativa L.) alfalfa floral volatiles were analyzed for honey bee antennal response using a combined gas chromatography-electroantennal detector system. All 10 alfalfa floral volatiles elicited antennal responses, and significant differences were observed in average honey bee antennal response to these 10 compounds. Linalool and methyl salicylate elicited "sticky" antennal signals (slow recovery toward baseline physio-electrical output). This "sticky" response may suggest a biologically active role for these two compounds. Support for a biologically active role for linalool and cis-3-hexenyl acetate comes from the chemical and structural similarity between these two compounds and two honey bee pheromones, geraniol (nasonov) and n-hexyl acetate (alarm), respectively. Selection for increased emanation of linalool and methyl salicylate, and decreased emanation of cis-3-hexenyl acetate, is suggested as a possible method for increasing the attractiveness of alfalfa to honey bees. Finally, significant differences were demonstrated in both among- and within-hive average antennal response to most of the volatile compounds. Based on the results of this study and those of other investigators, we hypothesize that host-pollinator interrelationships can be strengthened by directed selection in both honey bees and alfalfa