Identify Types of Bees: The Osmia Mason Bee

Bees of the Osmia genus are frequently called “Mason Bees,” and they’re most common in the western United States. They differ from other types of bees because of their unusual nesting habits.

| November 7, 2013

Osmia Mason Bee on a flower

Osmia females carry dry pollen in a patch of hairs (scopa) on the underside of the abdomen, a feature they share in common with other females in the family Megachilidae.

Photo By Rollin Coville

The Xerces Society, a nonprofit conservation organization, is a leader in the effort to conserve North America's native pollinators. Founded in 1971, the society protects insects and other invertebrates through advocacy, education, policy development and applied research projects aimed at protecting and managing critical habitat. Attracting Native Pollinators (Storey Publishing 2011), by The Xerces Society, is a complete action plan and information guide for protecting bees, wasps, butterflies, moths, flies and some beetles by providing flowering habitat and nesting sites.The following excerpt comes from Part 3: Bees of North America.

You can purchase this book from the MOTHER EARTH NEWS store: Attracting Native Pollinators

Osmia: Mason Bees


FAMILY: Megachilidae

SUBFAMILY: Megachilinae

Osmia are usually called Mason Bees because many of these types of bees construct walls of mud to divide the nest cavity into brood cells. The genus is large, with approximately 150 species in North America. Many species are widespread and abundant, but Osmia are rare in deserts. They are most common in the western United States; east of the Mississippi, there are only 27 species.

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