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Osmia californica Cresson, 1864


Scientific Name: Osmia californica Cresson, 1864

Common Name: California Mason Bee


Osmia californica Cresson, 1864: 24 [♀].

     Holotype ♀. USA, California, Fort Crook, by H. Ulke [ANSP no. 2514].

Osmia nassa Cockerell, 1910: 272 [♀]. Synonymy by Sandhouse (1939: 31).

     Holotype ♀. USA, California, Claremont, by Baker [USNM no. 13439].

Osmia occidentalis Michener, 1936: 42 [♀]. Synonymy by Sandhouse (1939: 31).

     Holotype ♀. USA, California, Mono County, Gull Lake, 11 July 1934, by J.E. Law [].


Taxonomic Notes: The ♂ was described by Rust (1974: 64).

Michener (1936: 42) indicated the similarity of his O. occidentalis Michener to both O. pascoensis Cockerell and O. nassa Cockerell, with only subtle differences in robustness and hair colour to the former, and puncture density and hair colour in the latter.

Though Sandhouse (1939: 22) distinguished female O. californica Cresson (and O. pascoensis Cockerell) from O. marginipennis Cresson based on clypeal puncture density (i.e., more sparse in the latter), Rust (1974: 71) indicated that the females of O. californica and O. marginipennis were indistiguishable. Rust (1974: 63) also synonymized O. pascoensis Cockerell under O. californica Cresson (both described from the female), but Parker (1980: 39) believed this was in error, indicating that O. pascoensis was a synonym of O. marginipennis Cresson. Parker (1980) distinguished O. marginipennis from O. californica mainly by hair colour, indicating all pale on tergum 1 (which does not always seem to be the case, as the basolateral area often have black hair in both species) and the more sparsely punctate medial area of the scutum in the former, which seems to be supported by COI.

DNA Barcode Index Number (BIN): BOLD:AAA7671

Biology: Several aspects of the nesting biology of this species were studied or summarized by Levin (1966), Rust (1974), and Torchio (1989a), who indicated that this species was unusual compared to other North American Osmia in that it used both mud and masticated plant material, as a mixture, for nest plug and partition construction, not one or the other, though Parker (1980) also reported this for O. marginipennis. Parker (1980) indicated that this species uses cohort splitting as a wintering strategy, with both adults and prepupae within a population wintering, a strategy similar to O. marginipennis. Cripps and Rust (1989) indiacted that this species was a Asteraceae specialist. Torchio (1989b) indicated that Stelis montana Cresson is a nest parasite.

Distribution in Canada: Criddle et al. 1924 [BC]; Sandhouse 1939 [BC]; Buckell 1950 [BC]; Rust 1974 [BC]; Elwell 2012 [BC]; Sheffield and Heron 2019 [BC].


Sheffield CS, Heron JM (2019) The bees of British Columbia (Hymenoptera: Apoidea, Apiformes). Journal of the Entomological Society of British Columbia 115: 44-85.

Criddle N, Curran CH, Viereck HL, Buckell ER (1924) The entomological record, 1923. Annual Report of the Entomological Society of Ontario 54: 87-102.

Michener CD (1936) Some western bees of the genus Osmia. The Canadian Entomologist 68(2): 39-43.

Buckell ER (1950) Record of bees from British Columbia: Megachilidae. Proceedings of the Entomological Society of British Columbia 46: 21-31.

Sandhouse GA (1939) The North American bees of the genus Osmia (Hymenoptera: Apoidea). Memoirs of the Entomological Society of Washington 1: 1-167.

Rust RW (1974) The systematics and biology of the genus Osmia, subgenera Osmia, Chalcosmia, and Cephalosmia (Hymenoptera: Megachilidae). The Wasmann Journal of Biology 32(1): 1-93.

Cockerell TDA (1910) New and little-known western bees. Entomological News 21(6): 270-273.

Parker FD (1980) Nests of Osmia marginipennis Cresson with a description of the female (Hymenoptera: Megachilidae). The Pan-Pacific Entomologist 56(1): 38-42.

Levin MD (1966) Biological notes on Osmia lignaria and Osmia californica (Hymenoptera: Apoidea, Megachilidae). Journal of the Kansas Entomological Society 39(2): 524-535.

Torchio PF (1989a) In-nest biologies and development of immature stages of three Osmia species (Hymenoptera: Megachilidae). Annals of the Entomological Society of America 82: 599-615.

Cresson ET (1864) On the North American species of the genus Osmia. Proceedings of the Entomological Society of Philadelphia 3: 17-38.

Cripps C, Rust RW (1989) Pollen preferences of seven Osmia species (Hymenoptera: Megachilidae). Environmental Entomology 18(1): 133-138.

Torchio PF (1989b) Biology, immature development, and adaptive behavior of Stelis montana, a cleptoparasite of Osmia (Hymenoptera: Megachilidae). Annals of the Entomological Society of America 82(5): 616-632.

Sociality: Solitary
Nesting: Cavity Renter
Pollen Specialization: Broad Oligolecty
Wintering Stage: Adult

Crop Preference: Not Available
Non Crop Preference: Not Available

Distribution: British Columbia
Ecozone: Western Interior Basin