The effect of prediapause temperature on diapause induction was investigated in a Michigan strain of the codling moth,Cydia pomonella(L.). A temperature of l7°C enhanced diapause induction, but higher temperatures averted or diminished the photoperiodic response. of the codling moth larva to diapause induction. The critical photoperiod (L:D) for 50% induction of diapause was 15:9, 14.4:9.6, 13.8:10.2, and 13.44:10.56 at 17, 22, 27, and 30°C, respectively. A method of estimating the diapause response of the codling moth to temperature is presented.