Last summer at Bodega Head, Sonoma County, I captured an image of what appears to be a yellow-faced bumble bee, Bombus vosnesenskii, nectaring on a bull thistle.
Was it?
It could be Bombus caliginosus, according to bumble bee expert John Ascher on iNaturalist.
Bohart Museum of Entomology research associate Tom Zavortink mused that it's difficult to distinguish between a vosnesenskii or caliginosus "without examining the length of the malar space, which is not visible in your photo. In fact, the difference in the length of the malar space in these species is so small that it is difficult to distinguish them even when specimens are available for examination."
The malar space is the area between the bottom of the compound eye and the top of the mandible.
If it is B. caliginosus, its common name is "the obscure bumble bee." It's a species native to the West Coast. Its distribution range extends from Washington through Oregon to southern California.
Wikipedia tells us: "This bumble bee has been noted on 19 families of plants. The workers ;are most often seen on Fabaceae, the legume family, while queens are most often seen on Ericaceae, the heath family, and males have been noted most often on Asteraceae, the aster family. Common plants visited by the workers in a sample included ceanothus, thistles, sweet peas, lupines, rhododendrons, Rubus, willows, and clovers. Queens emerge from hibernation in late January, the first workers appear in early March, and the males follow by the end of April. The colony dissolves in late October, when all the inhabitants die except the new queen."
BugGuide.net points out that the common name, Obscure Bumble Bee, "invites confusion with the Old World Bombus obscurus Seidl, 1838, a junior synonym of B. rupestris (Fabricius), and is not very informative as dozens of bumble bee species are more obscure than this one."
I'll just call it a "Bombus Beautiful." But then aren't all the some 250 species of the genus beautiful?
Cheers!
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