At a 1-m depth in the soil, temperatures remain at a relatively constant value (mean average of the surface temperature) with only a total daily fluctuation of 1°C. This temperature range was found to be practical for use in incubating insects that were treated with insecticides for toxicity studies, especially in resistance monitoring programs. Groups of 24 d-old male susceptible pink bollworms,Pectinophora gossypiella(Saunders), were mired in insecticide-laced sticky cards or placed in 20-ml scintillation vials coated with the following insecticides: fenvalerate, permethrin, and monocrotophos. When incubated in the bottom half of a hole in the ground 1 m deep outside of our laboratory at Riverside, Calif., in the middle of summer, results were comparable to incubation of similarly dosed insects in environmental chambers. Control mortality was negligible for pink bollworm adult males held in untreated scintillation vials at constant temperatures from 16.5 to 40°C for 2 d. Thus, storing treated insects in simple holes in the ground is a valuable new tool in resistance monitoring by eliminating the transport of insects away from field pheromone traps and other collection sites.