About two months ago, I noticed what looked like a C. semitestaceus nest right in the same location where I found this ant wandering around. Last week, I was back there again, and this time collected a worker as it wandered out of the nest in the middle of the day for some reason. It's pretty much the same color as this original one, a color of Camponotus I rarely see in the Santa Ana Mountains. So with that fact in mind, I also checked the GPS of both specimens, and they were in the exact same spot, so this new specimen is clearly from the same colony as the originally posted one.
Here's some better pictures of the new specimen and the nest.
Nest
These pictures clearly show flatted antennal scapes at the base, so I think this is definitely C. semitestaceus... unless of course, that isn't the only species that has that feature. Anybody know if this is true or not?