The range of temperatures of red imported fire ant, Solenpsis invicta Buren, foraging and food bait removal were examined in laboratory assays for six ant colonies collected from central Texas. Ants were observed crawling from laboratory colonies through clear plastic tubes traversing through a temperature controlled water bath in order to access and remove peanut butter bait. The minimum and maximum critical temperature range for these foraging S. invicta worker ants was 10 and 50°C, respecitvely. The results suggest that exclusion of ant activity can be attained using temperatures outside of this range. Maximum foraging and bait removal in these assays indicate that optimum temperatures for fire ant bait application are between 25° and 35°C. Using video recordings, crawling speed was found to vary for individual ants between the temperature extremes of 10° and 49°C, ranging from 0.21-cm/sec at 10°C to 3.46-cm/sec at 48°C. There was a significant linear relationship between speed and temperature (r² = 0.71), where Speed = −0.19 0.06 × Temperature.