Petals and leaves: quantifying the use of nest building materials by the world's most valuable solitary bee.

The alfalfa leafcutter bee (Megachile rotundata, hereafter simply "leafcutter bee") is a solitary, cavity-nesting bee native to Eurasia, managed as an agricultural pollinator of alfalfa and several other crops in North America since the 1940s (Pitts-Singer and Cane 2011). The most intensively managed and economically valuable solitary bee worldwide, it serves as a model organism for studying solitary bee biology (Pitts-Singer and Cane 2011). Understanding this species' nesting behavior is critical to its propagation for commercial pollination services. As its common name suggests, female leafcutter bees construct their nests in above-ground holes using carefully clipped pieces of leaves (Pitts-Singer and Cane 2011).