I would guess C. semitestaceous. What do you think? I say Camponotus, not Formica, because of the smooth single-humped thorax. This is confirmed by the fact that this ant let me focus on her for 3 1/2 minutes; Formica tend to be more skittish. Trail 15 in a leather oak (Quercus durata durata) in the serpentine, 10:45:06 am.