Several pure species (Cereus giganteus, Simmondsia chinensis, Prunus dulcis, Larrea tridentata, Populus fremontii) of pollen collected by honeybees (Apis mellifera) plus mixtures of bee-collected pollen were analysed for the presence of phagostimulants by feeding of extracts of them mixed with candy to caged bees and measuring the amounts consumed in comparison with a reference food. All species and mixes of pollen, even the poorly nutritive and unpreferred cottonwood pollen (P. fremontii) contained phagostimulants. Phagostimulants were found in extracts prepared with polar solvents, non-polar solvents, and solvents of intermediate polarity. Phagostimulants were found in all fractions collected from silicic acid column chromatography except the least polar fraction consisting mainly of hydrocarbons and other extremely non-polar compounds. Thus the results suggest that phagostimulants in pollen are not limited to one discrete class of compounds, and likely comprise a variety of compounds. Pollen consumption by bees is probably induced primarily by the cumulative effects of numerous compounds in pollen in the absence of specific repellents, rather than by one or a few specific compounds.
Pollen, Phagostimulants, non polar substances, polar substances