SummaryPopulation losses following relocation of nesting femaleMegachile rotundata, were studied under a variety of environmental conditions. Heavy losses (over 50%) occurred when bees were moved: from nesting sites with many prominent landmarks into alfalfa fields with few landmarks; from fields with abundant foraging blossoms into fields with little bloom; and when strong winds prevailed (over 48 km/h).Losses were much lower when bees were moved: with their original shelters, and into areas similar in landmark composition to the original nesting sites; with their original shelters through only a short distance (100 m); after conditioning to a coloured shelter before a short-distance move; into areas with sufficient bloom to maintain themselves; during periods of low wind speed (under 16 km/h).These results form the basis for recommendations for the commercial transfer of this leaf-cutter bee for alfalfa pollination.