Red and Black Carpenter Ants, Camponotus semitestaceus
These large, red and black carpenter ants are very common in the lower elevations, in the oak woodland areas.
The species is Camponotus semitestaceus, as identified by Dr. Philip S. Ward, 19 May 2017.
These ants are nocturnal, foraging at night. They do not excavate wood, which is common for many other carpenter ants. I have found colonies of these ants under rolled carpet, between sheets of stacked plywood, under rocks, at the base of live oak trees, and under the foil layer of fiberglass attic insulation. In one case, the ants were between the insulation that was cut out to fit over an attic access door, and the adjoining insulation over the ceiling, and they fell on me as I opened the attic door. Maybe the oddest nest location I have seen was on the inside wall of a large drainage pipe, after removing the manhole cover; the ants were simply holding onto the inside of the large pipe. So, these ants do little in the way of nest construction. Their large size, sometimes within and adjacent to human habitation nest locations, and large size, make them particularly annoying pests. The distribution range seems connected to the interior live oak areas.