~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)
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
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.
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
(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