Photoperiodic Reversibility of Diapause Induction in an Insect

Abstract
The diapause of the pink bollworm is under photoperiodic control. Diapause is prevented when the dark phases of the daily photoperiod are 8 to 10 hours in duration. If the dark period is extended to 12 hours, diapause is induced. Intercalation of 8- or 10-hour nights may reverse the diapause induction caused by exposure to photocycles having 12-hour dark phases. The 10-hour night was much more effective in reversing induction than the 8-hour night. The intensity of diapause, in part, appeared to be dependent on the previous photoperiodic experiences of the test animals.