My name is Dr Margriet Dogterom and am the founder and owner of Beediverse. I write this blog for all who love bees and who want to learn more about these wonderful creatures.
The Wasmann Journal of Biology (Vol 32 no 1 1974) has an excellent article on a variety of bee species including Osmia californica. It includes range maps of Osmia species. The known distribution of Osmia californica is in western North America and eastwards to Montana and Colorado (including British Columbia, Washington, Oregon, California, Idaho,Wyoming, Utah, Nevada) but not in Arizona or New Mexico.
Female color is metallic blue black, legs black to reddish black. The mandibles have 4 teeth.
Male is black to metallic blue black.
The male and female varies from entirely black to black with white tufts and areas of intermixed black and white.
It appears as early as May in the southern and warmer location and as late as August in higher altitudes.
Biology: The egg is located in the center of the pollen store, with the store usually filling the cell. The cell and plug partitions are constructed of small pieces of masticated leaf and mud. The amount of leaf varied from 1% to 50% of the partition. The partitions were tough, with the outer surface shallowly concave and smooth. The inner surface was rough and the spiral ring construction was easily seen.
This is a great link to view coloured photos of mason bees pests.
Finding anything written about Osmia californica is not easy. Although I found an article written on californica by M. D. Levin, his scientific article was published in the Journal of Kansas Entomological Society, 1966. Unless you are affiliated with a university, only the abstract is available. I will write a summary of the article when I get the full article. But I did find a great web site with good and very detailed photos of Osmia californica. Link to photos of Osmia californica