Nectar and pollen sugars constituting larval provisions of the alfalfa leaf-cutting bee (Megachile rotundata) (Hymenoptera: Apiformes: Megachilidae)

As with most solitary bees, larvae of the alfalfa leaf-cutting bee, Megachile rotundata Fab., eat a diet blended from pollen and nectar of unknown proportions. In this study, we developed protocols to isolate and quantify sugars from larval provision masses. The method removed free amino acids that leach from pollen and confound chromatography, but without autohydrolyzing sucrose. Pollen sugars were a negligible fraction of provision mass sugars. Glucose and fructose constituted about half of the provision fresh weight. Sucrose in alfalfa pollen and nectar is absent from the provision, presumably enzymatically hydrolyzed to glucose and fructose in the provision. Provision masses are composed of two to three times more floral equivalents in pollen than nectar. Female M. rotundata, and other solitary bees with pasty provisions, gather proportionally more pollen than nectar compared with the resource needs of colonies of social honeybees and bumblebees.