Bees on the butterfly weed

Here is the Asclepias tuberosa I planted last July, hoping to support butterflies. I was so pleased to see that it survived to grow and bloom this year. At first I didn’t see any insects visiting it, but today noticed three different small bees on it, two of which are visible in this photo. The few butterflies we’ve had lately have focused on the butterfly bushes, and the little zinnias that have begun to bloom.