Newly emerged Tenebrio molitor were reared at 4, 25, and 37°C in nutrient media supplemented with sodium selenate (0.0125, 0.0200, 0.0500, and 0.1000%). Ten insects comprised each group. Controls were maintained in unsupplemented medium at the same temperatures as the experimental groups. Survival percentages were determined. Survival curves were estimated at given times postincubation. Controls at 4 and 37°C showed an increased lethality compared to those insects at 25°C. Data indicate that 4°C had a protective effect on survival for insects reared in media containing the three highest concentrations of selenium. For insects at 37°C, killing was striking and equivalent for all groups, irrespective of media supplementation.