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Genus Osmia - Mason Bees

Bee - Osmia integra Osmia? - Osmia montana Osmiini 01b - Osmia coloradensis - female bee - Osmia distincta - female Bee house, the next generation - Osmia cornifrons - male Bee - Osmia lignaria - female Metallic green bee - Osmia ribifloris - male Mason Bee - Osmia taurus - male
Kingdom Animalia (Animals)
Phylum Arthropoda (Arthropods)
Subphylum Hexapoda (Hexapods)
Class Insecta (Insects)
Order Hymenoptera (Ants, Bees, Wasps and Sawflies)
No Taxon (Aculeata - Ants, Bees and Stinging Wasps)
No Taxon (Anthophila (Apoidea) - Bees)
Family Megachilidae (Leafcutter, Mason, and Resin Bees, and allies)
Subfamily Megachilinae (Leafcutter, Resin, Mortar, Sharptail, Mason, and Woolcarder bees and relatives)
Tribe Osmiini (Mason bees and relatives)
Genus Osmia (Mason Bees)
Explanation of Names
Author: Panzer, 1806
~150 spp. in 9 subgenera our area, >350 spp. in 23 subgenera worldwide(1)
Metallic green, blue or blue-green, with short, robust body.
Key to genera of the Western Hemisphere on pg. 478 of Michener(2)(2007).

Osmia are metallic, sometimes all black but never red or yellow striped. There is no pygidial plate on Osmia.(3)

Osmia have parapsidal lines which are actually points or small holes rather than lines. Discover Life has these shown with arrows. And in this photo they are visible on a specimen. (3)

Unique to Osmia is the arolium between the front claws. Notice the back claw in this one and the front claw in this one
Holarctic, with 1 sp. ranging into the Neotropics [map](1)
Most species early-late spring, a few active in summer.
(starts flying in Jan. in sw US, and in Mar. elsewhere)
Many species visit Vaccinium, including blueberries, and other Ericaceae.
Variety of nesting; some excavate in the soil, others use hollow stems, some use abandoned mud wasp nests. They partition the cells with walls made of clay or other materials.
Print References
Michener, Charles D. (1949) A Revision of the American Species of Diceratosmia (Hymenoptera, Megachilidae). Annals Ent. Soc. Amer., 42(3): 258-264 (Full Text)
Rust, Richard W. (1974). The systematics and biology of the genus Osmia, subgenera Osmia, Chalcosmia and Cephalosmia (Hymenoptera: Megachilidae). Wasmann Jour. Biol. 32: 1-93 (Full Text)
Sandhouse, Grace A. (1924). Bees of the genus Osmia in the collection of the California Academy of Sciences. Proc. Calif. Acad. Sci. (4) 13: 341-372 (Full Text...early key to western species on pg. 357)
Sandhouse, Grace A. (1939). The North American bees of the genus Osmia. Memoirs of the Entomol. Soc. Wash. 1: 1-167.
Sinha, Ranendra N. (1958). A subgeneric revision of the genus Osmia in the Western Hemisphere (Hymenoptera: Megachilidae). Kans. Univ. Sci. Bul. 39 (5): 211-261 (Full Text)
Sinha, R. N. & C. D. Michener (1958). A revision of the genus Osmia, subgenus Cetrosmia (Hymenoptera: Megachilidae). Kans. Univ. Sci. Bul. 39 (7): 275-303 (Full Text)
Snelling, Roy R. (1967). Description of a new subgenus of Osmia (Hymenoptera: Megachilidae). Bull. of the Southern Calif. Acad. of Sci. 66: 103-108 (Full Text)
White, Jimmy R. (1952). A revision of the genus Osmia, subgenus Acanthosmioides (Hymenoptera: Megachilidae). Kans. Univ. Sci. Bul. 35: 219-307 (Full Text)
Works Cited
1.Ascher J.S., Pickering J. (2017) Discover Life bee species guide and world checklist (Hymenoptera: Apoidea: Anthophila)
2.The Bees of the World, 2nd edition
Charles D. Michener. 2007. The Johns Hopkins University Press.
3.The Bees in Your Backyard: A Guide to North America's Bees.
Joseph S. Wilson & Olivia J. Messinger Carril. 2015. Princeton University Press.