The Alfalfa Leafcutter Bee (Megachile rotundata) is a European species of bee that has been cultured in the United States for pollination purposes and has also become feral and widespread. As a solitary but gregarious bee species, it does not build colonies or store honey, but is a very efficient pollinator of alfalfa seed, carrot seed, and some other vegetables.
Alfalfa leafcutter bees have stingers, but they often use their mandibles as a defensive mechanism, and only defend themselves when squeezed. Thus bee suits, such as those required with honey bees, are not necessary when dealing with leafcutter bees. The ratio of males to females is generally one to one.
Females in the wild create nests in small holes in the ground or in available cracks/crevices in trees or buildings. The nests are composed of a string of individual cells, as many as the space will allow. When managed for pollination, the females are induced to nest in drinking straws or drilled blocks of wood.
Each cell is made from circular disks cut from plant leaves using the bee's mandibles, hence the name "leafcutter". While the bees do not store honey, females do collect pollen which they store in the cells of their nests. Each cell contains one pollen ball and one egg. The larva develops rapidly, consuming the pollen ball and entering hibernation when the pollen is fully consumed. The next spring, the mature larva pupates and completes its development. Once the bee is developed it cuts its way out from the nest. The incubation period is approximately 30 days and requires a constant temperature of greater than 30°C (86°F).