Quite a few beewolves were feeding on Pycnanthemum tenuifolium (Narrow-leaf Mountain mint) blossoms at the border between a long-established tall grass prairie planting and a native black oak grove -- all in a sand area. Some did not appear to me to be P. gibbosus -- these were a bit larger and more robust, and the yellow marking on the 2nd terga had a substantial gap as in the photos here of P. lunatus and P. lepidus. Also, when reviewing the photos they are not obviously dimpled. Reviewing the photos, I have at least two individuals and have separated them, though they may be the same species. I didn't see these on any flower other than P. tenuifolium even though there were many others in bloom.