Yellow-faced Bumble Bee,  Bombus vosnesenskii

The yellow faced Bumblebee is a fat black bee that is relatively slow and easy to photograph. A couple of time I thought the bee was dead, no, just slow.
Bombus vosnesenskii lives from about San Diego throughout most of California(except the desert areas), a little into Nevada around Reno,  through Oregon, Washington up into Osoyoos British Columbia.
This bumblebee is largely as summer bee with most of the hive living from April to September and is the most common bumblebee of California. Bombus caliginosus is very similar and very hard to tell apart, even if you have a dead bee in hand. Since we're trying encourage people to plant plants to save them, a pin through the middle of them seems to be a buzz killer.

Imagine your whole life in a few months, everything accelerated. We must seem as slow as a tree to them.
This bumblebee nests in the ground, commonly in old gopher holes.We had a large colony in the pile of fifteen gallon pots. The bees flew in through the drainage hole and filled about half of a bucket. We heard them for the whole summer, but didn't figure out what was happening until the next winter when we used some of the pots and found the old nest.
Bumble bees have a wicked sting, and they can sting repeatedly. BUT, I've only been stung when I stepped on one bare footed and when I had one land on my neck and I smashed it. Both times the bee lived, I didn't.
Nectar sources include, (not limited to), Arbutus, Agastache, Arctostaphylos, Astragalus, Aster,  Brodiaea, Berberis(Mahonia), Castilleja, Ceanothus, Cercis, Chrysothamnus, Cirsium, Clarkia, Crataegus, Dicentra, Epilobium, Eriastrum, Eriogonum, Eschscholzia, Grindelia, Helenium, Heteromeles, Horkelia, Iris, Isomeris, Malacothamnus, Marah, Mentha, Mimulus, Monardella, Nama, Orthocarpus, Penstemon, Phacelia,  Potentilla, Prosopis, Prunella, Prunus, Ranunculus, Rhamnus, Rhododendron, Rhus, Ribes, Salix, Salvia, Senecio, Sidalcea, Solidago, Sphaeralcea,  Symphoricarpos, Trichostema, Trifolium, Vicia, Wyethia
Forage probably ranges over 500 meters, with mean about 275 meters(.Osborne et. al. 1999)
Syn. Bremus vosnesenskii, Bombus columbicus

Osborne, et. al. 1999, A landscape-scale study of bumble bee foraging range and constancy, using harmonic radar.   Journal of Applied Ecology, 36, 519-533
Thorp, Robbin W., & Horning, Donald S. & Dunning, Lorry L.  1983  Bumble bees and cuckoo bumble bees of California (Hymenoptera, Apidae) / by Robbin W. Thorp, Donald S. Horing, Jr., Lorry L. Dunning  University of California Press, Berkeley.