Masked bees (Hymenoptera: Colletidae: Hylaeus spp.) get their common name from the yellow or white markings that adorn their black faces. Like other bees they spend a great deal of time collecting pollen and nectar from flowers. While they consume some of this food, the excess is transported back to their nests to provision their young. The particular masked bee shown here was busy at work on the flower of a sulphur cinquefoil (Potentilla recta, Rosaceae).
Most bees possess external structures that help them transport pollen back to their nests. Some have scopae, which are dense brush-like collections of hairs on their rear legs or abdomens. Others like honey and bumble bees have basket-like structures on their hind legs called corbiculae. Mining bees have neither of these, and instead transport pollen and nectar using only a honey stomach. This enlarged area of the esophagus is located just ahead of the “regular” stomach. Pollen and nectar stored here can be easily regurgitated once the bee returns to its nest.