Ecology of the Leaf-cutter Bee Megachile perihirta Ckll. (Hymenoptera: Megachilidae) in Relation to Production of Alfalfa Seed

The relative importance as pollinators of alfalfa of each of the 14 species of Megachile that occur in southern Alberta has been assessed on the basis of Alberta distribution, frequency and abundance in mixed prairie, nesting habits, pollen preferences, and flight period; two ground-nesting species of the subgenus Xanthosarus Rob., Megachile perihirta Ckll. and M. dentitarsus Slad., were judged the principal pollinators (Hobbs and Lilly, 1954).