 many trips to flowers to gather sufficient resources to provision a single brood cell. Of course with more, more pollination is accomplished.
North America has many native megachilid species, but Alfalfa leafcutter bees (Megachile rotundata) are an imported species used for pollination. The most significant native species is Osmia lignaria (the "Orchard Mason Bee" or "Blue Orchard Bee"), which is sold commercially for use in orchard crop pollination, and which can be attracted to nest in wooden blocks with holes drilled in them (which are also sold commercially for this purpose).
Leafcutter bees nest in soft, rotted wood; thick-stemmed, pithy plants (e.g., rose); and in similar materials that the bees can easily cut through and excavate. Nest tunnels may extend several inches deep and coarse sawdust may be deposited at the entrance. This sometimes causes confusion with other wood nesting insects such as carpenter ants. However, leafcutter bees restrict their tunneling to soft, rotted wood and do not cause damage to homes or other wooden structures.
There also are concerns about leafcutter bee nesting in rose canes, excavating the pith of pruned canes. Leafcutter bees sometimes nest in the largest diameter rose canes but cause little damage because they restrict tunneling to the pith and rarely girdle cambium. Furthermore, other insects, including various hunting wasps (Pemphredon species) and small carpenter bees more commonly tunnel and nest in rose canes.
After the nest is made, the bees collect fragments of leaves to construct individual nest cells. The bees cut leaves in a distinctive manner, making a smooth semicircular cut about 3/4 inch in diameter from the edge of leaves. Although they cut many types of leaves, leafcutter bees prefer certain types, notably rose, green ash, lilac and Virginia creeper. This injury often is only a minor curiosity. However, where leafcutter bees are abundant and concentrate on cultivated plantings, the removal of leaf tissues can be damaging. Serious damage most often occurs