Abstract
Large nymphs of Periplaneta americana preconditioned at different temperatures were treated externally or by injn. with DDT. Roaches stored at temps, which produce relatively saturated lipids are markedly less resistant to DDT than are roaches stored at temps, which produce relatively unsaturated lipids. Roaches stored at very low temps, for over 2 weeks show an increased susceptibility to DDT. Female nymphs are more resistant to DDT than male nymphs. A theory to explain the above results is offered.