Hylaeus strenuus, a recently introduced bee from India. Keaau Valley, Makua-Keaau FR. It is blowing out a drop of wiliwili (Erythrina sandwicensis) nectar to concentrate it before returning to its nest. Erythrina are bird-pollinated and have relatively dilute nectar, meaning it's inefficient for them to carry it without concentrating. No other bees here seem to visit it.