Cindy told me there was a rare plant blooming at Jasper Ridge. It was in an interesting place: the disturbed land between Monica's Bench and the road, near the Sun Research Center. While capturing macros of the plant and its flowers, I noticed a bee-like fly pollinating the Tarweed.
The rare plant is Lessingia hololeuca. Thanks to Pierre Martineau for helping ID the fly: a Hover Fly, specifically a female Syrphid Fly (Taxomerus marginatus). I discovered lots of info about it, and about flies in general, on the web.
More info on the Hover Fly is at images 16( ID), 17 (halteres), & 27 (female). A question -- extra eyes? -- is at #24. (Now Pierre Martineau has answered the question and explained the 5 eyes of most insects!) Other unidentified insects are at images #36ff & 41. Thanks to all for your comments and help with IDs.