Harvester ants,Pogonomyrmex owyheeiCole, irradiated with 3.5 kR to 268 kR of 137Cs gamma radiation, were maintained at simulated summer (27°C) and winter (7°C) temperature regimes. After thirty days, the cool series was warmed to 27°C and observed for mortality along with the warm series. Though mortality was delayed in the cool series, each series reached 50% mortality at similar rates.Because the harvester ant is extremely tolerant to radiation and experimental rates used far exceed possible environmental exposure, it is unlikely that ant colonies dwelling among low-level nuclear waste storage sites will be deleteriously affected by radiation. This species has the capability of tunneling to a depth well within the range of some buried waste. Since these harvester ants are potential transporters of buried waste, they should be considered as a biotic factor in radioactive waste management operations in semi-arid regions.