Abstract:The effects of constant and changing photoperiod on nymphal development are investigated to understand the seasonal life-cycle strategy of a nymph-overwintering cricket, Velarifictonus ornatus, in Zhuzhou, Hunan. Nymphal development was slow under constant photoperiods at 25℃. The shortest mean duration of nymphal development was (2062 ± 44.0) (mean ± SD) days at LD 16∶8 h, followed by (230.3±47.4) days at LD 12∶12 h and (236.5±933) days at LD 14∶10 h. No significant difference was observed in the nymphal durations among different constant photoperiods at 25℃. Nymphal development was further prolonged when nymphs were exposed to LD 16∶8 h during the first 60 days and then transferred to LD 14∶10 h or LD 12∶12 h at 25℃. Similar results were obtained when nymphs were transferred from LD 14∶10 h to LD 12∶12 h at 60 days after hatching at 25℃. However, in the reverse transfer, i.e. from short days to long days, the durations of nymphal development was dramatically shortened. When nymphs were transferred from LD 12∶12 h to LD 16∶8 h at 10, 30, 60 or 90 days after hatching, the mean nymphal durations were (135.9±885), (80.0±5.9), (110.4±10.4) and (142.9±10.8) days respectively. When photoperiod was shifted from LD 12∶ 12 h to LD 14∶10 h at 60 days after hatching, the nymphal duration was (120.9±7.7) days. Nymphs exposed to those photoperiodic shift developed faster than those kept at constant photoperiods. Although adults emerged more rapidly under long days than those reared under short days at 30℃, changing photoperiods showed similar results on nymphal development as those at 25℃. These results suggested that seasonal changing day-length controls nymphal development of V. ornatus to synchronize their life-cycle with the season.