sentences:  "M. rotundata" was unintentionally introduced into the United States during the 1940s, and its management as a pollinator of alfalfa has led to a three-fold increase in seed production in the U.S.The synchronous emergence of the adult bees of this species during alfalfa blooming period in combination with such behaviors as gregarious nesting, and utilization of leaves and nesting materials that have been mass-produced by humans provide positive benefits for the use of these bees in pollinating alfalfa.Considerable research and development has been done with this important plant.