Megachile rotundata

Adults have a robust, cylindrical body that is mostly black with white bands on the abdomen.

The alfalfa leafcutting bee comes originally from southwestern Asia and southeastern Europe.

It was accidentally introduced into the United States by the 1940s.

It is thought to have arrived as pre-pupae hidden in tunnels inside wooden pallets.

Gregarious nesting, with many females nesting close together, is one of the traits that made it suitable for commercial management.

The young spend the winter as non-feeding pre-pupae, a resting larval stage.

In most of North America, adults emerge and mate in June and July.

Each nest cell is built from cut leaf pieces, usually 14 to 15 per cell.

It is polylectic, meaning it collects food from many different kinds of plants.

In a US study, female alfalfa leafcutting bees tripped (opened) 78% of the alfalfa flowers they visited; honey bees tripped only 22%.

Managing this bee in nests transformed the North American alfalfa seed industry, tripling seed production.

The most common way to manage it is the loose cell system, in which cocooned bees are taken out of the nest cavities for cleaning and storage.

Besides alfalfa, it is used to pollinate canola for hybrid seed, native legumes and blueberries.

Managed populations can be affected by many fungal diseases, including the fungus that causes chalkbrood.