Alfalfa Leaf Cutter Bee – Megachile rotundata

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It is smaller than our native megachiles (5-9mm long rather than 9-20). It is a stocky bee with a broad head. Under the abdomen of the female is a ventral brush furnished with short, coarse, silvery gray hairs.

Life cycle

Adult bees emerge from individual cells where they have overwintered. Mating takes place as soon as the females emerge, which emerge after the males.

The female builds her own nest and takes care of her food supply. It can nest in various cavities, dig a nest in the ground or use a nest box.

The female builds eight to 12 cells per nest, depending on the length of the cavity. The cells, arranged end to end, are made from pieces of leaves or petals cut by the bee. When a cell is completed, the beetle stuffs it with pollen and nectar and lays an egg in it. Once the nest is finished, the insect plugs its end. Each female can build more than one nest.

The larva that comes out of the egg is white. Its cell contains enough food for its development. It spends the winter in this shelter, at a stage called the prepupa (last stage of development of the larva). When sunny days return, the insect metamorphoses into a nymph and then into an adult.

Geographical distribution

Megachile rotundata is a naturalized species very well established in Quebec. Its use in various cultures favors its dispersal in the province.


This megachile frequents cultivated areas, but it is also found in urban areas, and even in city centers. It can live in a variety of human-modified habitats (infill or road edges).


The larva feeds on pollen and nectar.

What you need to know

The alfalfa leafcutting bee is the subject of significant commercial farming. It is used in various countries as a pollinator of alfalfa, a purple flowering plant cultivated for its seeds or as a forage plant. Canada is the world’s largest producer and exporter of Megachile rotundata cocoons .

This bee accepts the removable nesting boxes that are made available to it. These most often consist of a series of fluted polystyrene panels, which form several tunnels where the females build the nests. This free cell rearing system allows the extraction of cocoons in the fall.

A female takes about 2.5 hours to make a cell, in good conditions. It then takes five hours to supply it with food. There is therefore an average of 7.5 hours per cell, and the bee generally builds only one per day.

Ecological roles

These bees are important pollinators in natural, agricultural and urban environments. They serve as food for various animals.

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