Delay and acceleration of breaking diapause of Antheraea pernyi and Laspeyresia pomonella by photoperiod manipulation

Diapause of pupae of a silkworm, Antheraea pernyi Guerin-Meneville, was invariably terminated by exposure to cycles of 16 hours of light and 8 hours of darkness. When 15 minute light breaks were introduced during each 8 hour dark period at 21 hours after the beginning of the 16 hour photophase, 33 percent of the pupae did not break diapause. Diapause was broken in 67 percent of the pupae maintained in complete darkness. A similar light break introduced during a 12 hour dark period and a light break of one hour during a 14 hour dark period were not effective. Larvae of the codling moth, Laspeyresia pomonella (L.) had a similar pattern of response, but the percentage breaking diapause was always less. A biochemical mechanism which provides a possible explanation of the results with the oak silkworm is presented.