sentences:  Alfalfa seed production requires the presence of pollinators when the fields of alfalfa are in bloom.Alfalfa pollination is somewhat problematic, however, because western honey bees, the most commonly used pollinator, are less than ideal for this purpose; the pollen-carrying keel of the alfalfa flower trips and strikes pollinating bees on the head, which helps transfer the pollen to the foraging bee.Western honey bees, however, do not like being struck in the head repeatedly and learn to defeat this action by drawing nectar from the side of the flower.