Abstract
Long-day (LD = 18 light: 6 dark) and short-day (SD = 12L:12D) photoperiodic treatments of various sequences and durations were applied to Coleophora laricella (Hbn.) larvae at 20 °C. Continuous development did not occur at either constant LD or SD. At LD, growth of young larvae was slow and was suspended in the late second or early third instar. At SD, young larvae developed rapidly but entered diapause in the late third instar. Pupation occurred when LD followed a period at SD. Timing and synchrony of pupation in a population were shown to be controllable by specific LD and SD sequences.