I believe these are Apodemia mormo cythera, a late summer/fall-flying metalmark that is single-brooded.
Each of these photos is from Grizzly Flat in the western San Gabriels, August 2, 2008.
Apodemia mormo cythera. I'm putting a few up to show the variation, but most had more orange than multiple-brooded virgulti virgulti does.
Apodemia mormo cythera from Grizzly Flat. A friend, David Horner, regularly visits this area. The key to identifying them as cythera, besides the extensive orange, is the fact that they didn't fly earlier in the spring or summer as Behr's Metalmark does elsewhere (as up Mt. Baldy canyon). This population uses fasciculatum and we're almost sure these are single-brooded, and as single-brooded late flyers they belong with mormo. Next year I hope we'll be able to confirm this by watching for larvae and watching the adult emergence circa July.
A ventral view of Apodemia mormo cythera from Grizzly Flat.
Apodemia mormo cythera from Grizzly Flat.