Foragers were active on the insolated surface between sand surface temperatures of 27 -67 C. At 51 C foragers periodically paused in relatively cooler thermal refuges, such as by remaining in the shade or by climbing above the desert floor on any available object. The frequency and length of pauses in thermal refuges increased with increasing surface temperature. Workers, because of their small size (-4 mg live mass), had low thermal inertia, as evidenced by high cooling rates in a range of air speeds, and were therefore efficient heat exchangers, equilibrating rapidly to ambient temperature. Keywords: Namibia, Namib Desert, Kuiseb River, desert ants, desert adaptation, arid environment, foraging behaviour, Ocymyrmex barbiger, microclimate, animal behaviour, heat stress, temperature, thermoregulation.