In the leaf beetle Zygogramma suturalis the photoperiodic reaction of long-day type is revealed. The photoperiod acting from the beginning of adult life affects the ratio of diapausing and reproducing females, the duration of egg maturation and the oviposition period. At 20-23 oC the short photoperiod induces the diapause in 70% of the individuals. The termination of oviposition is controlled also by short day length. Ovipositing, overwintering and non-overwintering females differ in the norm of the short-day response. The temperature corrects the dates of occurrence of autumn-winter diapause after reproduction and affects the expression of spring diapause in overwintering females.Probably in the control of the seasonal development of the leaf beetle together with the environmental factors the endogenous, spontaneous processes take part.