Leaf-cutter bees (Megachilidae) are productive pollinators for many flowering plants and like most of our native bees, are solitary. Even if not seen cutting or carrying leaves for their nest, leaf-cutters are easy to identify by the way they carry their pollen. A leaf-cutter bee’s pollen-carrying structure (called a scopa) is on their abdomen. These bees seem to “swim” on flowers, rubbing their abdomen over pollen structures, collecting it on their scopa.
Unlike many other bee species, leaf-cutters do not mix nectar and salivary secretions with the pollen they are collecting (creating a pollen “paste”) before transporting it. This causes the pollen to be loosely packed in their scopa and much can fall off as the bee visits flowers, making for very good pollination.
You can easily see individual pollen grains this bee has collected because she did not create a pollen “paste”. Evening primrose flowers must release much of their pollen when they wither because bees more actively visit them in this state than when they are in full bloom.