Megachile rotundata

Definition

A solitary leafcutting bee (Hymenoptera: Megachilidae), commonly called the alfalfa leafcutting bee, native to Europe and widely introduced as a managed pollinator. Females construct individual nests in pre-existing cavities, lining brood cells with circular leaf pieces cut from host plants; cells are provisioned with pollen-nectar masses and sealed with additional leaf discs. The species exhibits pronounced sexual dimorphism and is the primary pollinator deployed in commercial alfalfa seed production, where its sonication behavior (buzz pollination) efficiently releases pollen from alfalfa's tripping mechanism. Unlike social bees, M. rotundata does not form colonies or store honey, and its sting is considered less painful than that of Apis mellifera.

Etymology

Megachile: Greek megas (large) + cheilos (lip), referring to the enlarged cutting mandibles of females; rotundata: Latin rotundus (round, circular), alluding to the neatly circular leaf pieces used to construct nest cells.

Example

In the irrigated alfalfa seed fields of the Pacific Northwest, farmers distribute cardboard tubes or boards drilled with 6 mm holes—each stocked with diapausing M. rotundata prepupae—to establish local populations that emerge and pollinate synchronously with crop bloom.

Synonyms

• Alfalfa leafcutting bee
• alfalfa leafcutter bee

Related Terms

• Megachilidae
• leafcutting bee
• solitary bee
• managed pollinator
• buzz pollination
• brood cell
• Sexual dimorphism
• pollination ecology
• Megachile

Usage Notes

The common name 'alfalfa leafcutting bee' is preferred in agricultural contexts; 'rotundata' distinguishes it from congeners such as M. pugnata and M. relativa. The species is often reared commercially and shipped as prepupae in diapause. Not to be confused with the alkali bee (Nomia melanderi), another solitary alfalfa pollinator with different nesting biology.