These interesting little bees cut pieces of leaf from plants to create a tubular nest case in which they lay their eggs and provision it with food before sealing it off with a perfectly circular piece of leaf at either end. They usually make their nests inside wood, such as wooden decks, benches, trees, but will also use bee boxes. They also sometimes create their nests under stones and that is where I have found their nest cases. These bees also, unlike many or even most, bees, carry pollen on their belly (can you see the yellow pollen?)