DIAPAUSE IN NEUROPTERAN CHRYSOPA OCULATA

Chrysopa oculata has a facultative diapause in the third instar within the cocoon. At 24 ± 1°C diapause was induced when both second and third instars experienced short-day (LD 12:12), whereas continuous development was promoted when either of these two stages experienced long-day (LD 16:8). Little difference was shown in the developmental rates of prediapause and non-diapause stages reared under the two photoperiods. At 24 ± 3°C the critical daylength for the Ithaca population was between 12·5 and 13·5 hr of light, whereas the critical photoperiod for larvae reared out of doors feel between 12·25 and 13·5 hr of daylight. Diapause was terminated when cocoons were transferred to long-day before they had been in short-day for 4 weeks. However, after 8 weeks, transfer to long-day had no effect and diapause ended even under diapause inducing conditions. Larvae in the field had almost completed diapause development by February. The results suggest that under natural conditions diapause is primarily induced by the short-days of late summer, that it is maintained by the short-days of fall and early winter, that diapause development occurs under short-day, and that the seasonal timing of development by overwintering larvae is determined by the temperature requirements of the insect and the seasonal temperature accumulations. © 1969.