POLLEN PREFERENCE AND ITS RELATIONSHIP TO NESTING SUCCESS OF MEGACHILE-ROTUNDATA (HYMENOPTERA, MEGACHILIDAE)

Estimations of pollen preference and nesting success were obtained whe n the alfalfa leafcutting bee, Megachile rotundata (F.), was exposed t o 11 crop species. M. rotundata exhibited some preference for the majo rity of these species, but significant preferences were observed only for bird's-foot trefoil and crown vetch pollens. Although this graded preference response indicated the general acceptability of each specie s as a pollen source, it was not directly related to nesting success. Preferred pollen sources did not increase the numbers, size, and survi vorship of offspring produced in the subsequent generation, but less p referred sources commonly contributed to lower levels of nesting succe ss. M. rotundata demonstrated the highest level of nesting success whe n exposed to the moderately preferred sainfoin.