Mason Bee

Mason bee is a name now commonly used for species of bees in the genus Osmia, of the family Megachilidae. Mason bees are named for their habit of using mud or other "masonry" products in constructing their nests, which are made in naturally occurring gaps such as between cracks in stones or other small dark cavities. When available, some species preferentially use hollow stems or holes in wood made by wood-boring insects.[1]

Species of the genus include the orchard mason bee O. lignaria, the blueberry bee O. ribifloris, the hornfaced bee O. cornifrons, and the red mason bee O. bicornis. The former two are native to the Americas, the third to eastern Asia, and the latter to the European continent, although O. lignaria and O. cornifrons have been moved from their native ranges for commercial purposes. Over 300 species are found across the Northern Hemisphere. Most occur in temperate habitats within the Palearctic and Neartic zones, and are active from spring through late summer.[2]

Osmia species are frequently metallic green or blue, although many are blackish and at least one rust-red. Most have black ventral scopae which are difficult to notice unless laden with pollen.[1] They have arolia between their claws, unlike Megachile or Anthidium species.[1]