Pollen host selection by predominantly alpine bee species of the genera Andrena, Panurginus, Dufourea, Megachile, Hoplitis and Osmia (Hymenoptera, Apoidea)

The pollen host selection by 19 bee species, which have their main Central European distribution in the Alps, was assessed by microscopical analysis of the scopal contents of about 900 females from museum and private collections. The results of the pollen analyses were complemented by a literature survey as well as by field observations. The examined species widely vary in pollen host spectrum and specialization, revealing a fascinating diversity in bee host plant use. Observed patterns of host plant choice range from narrow specialists, which exclusively collect pollen from the flowers of a single plant genus, to pronounced generalists, which harvest pollen from the flowers of up to 17 different plant families. A quantitative character is given to separate the morphologically very similar females ofPanurginusherziandP.montanus.