What North American Bees Are Associated With Milkweed (Asclepias) Flowers?

Recent interest in protecting pollinators has led many organizations to plant milkweed to support monarch butterflies. However, little is known about what bee species might also benefit from milkweed plantings. Here I compile a list of bee species that have been collected on milkweed flowers. I compiled these data by searching large online databases and regional collections and supplementing with field collections. At least 282 different bee species have been collected on milkweed. Milkweed flowers can provide an important nectar resource for foraging bees, particularly in arid regions and in dry times of the year.