Megachilidae

Megachilidae is a family of bees in the order Hymenoptera, comprising about 4,000 described species found worldwide. The group includes two subfamilies, Megachilinae and Osmiinae, and contains several well-known genera such as Megachile (leafcutter bees), Osmia (masonry bees), and Anthidium (carder bees).

A distinctive characteristic is pollen packaging: females carry pollen on the underside of the abdomen in specialized structures called scopa, rather than on the hind legs as in many other bees. This trait influences foraging and nesting behavior.

Nearly all Megachilidae are solitary, though some instances of communal nesting occur. They are cavity nesters, using hollow stems, twigs, holes in wood, or man-made nesting boxes. Nesting materials vary by lineage: leafcutter bees cut circular pieces from leaves to line brood cells; mason bees seal cells with mud; carder bees line nests with plant fibers or hairs. A few species are kleptoparasites, such as those in the genus Coelioxys, which lay eggs in the nests of other Megachilidae and exploit the provisions.

Megachilidae are important pollinators, including many agricultural crops and wild flora. Some species are oligolectic, collecting pollen from a narrow range of plants, while others are generalists. They are distributed worldwide in a range of habitats from forests and meadows to urban gardens.

Conservation concerns include loss of nesting sites and pesticide exposure, which can reduce populations. Efforts such as providing bee hotels or nesting blocks can support Osmia and related genera.