Optimal Low Temperature and Chilling Period for Both Summer and Winter Diapause Development in <em>Pieris melete</em>: Based on a Similar Mechanism

The cabbage butterfly, Pieris melete hibernates and aestivates as a diapausing pupa. We present evidence that the optimum of low temperature and optimal chilling periods for both summer and winter diapause development are based on a similar mechanism. Summer or winter diapausing pupae were exposed to different low temperatures of 1, 5, 10 or 15°C for different chilling periods (ranging from 30 to 120 d) or chilling treatments started at different stages of diapause, and were then transferred to 20°C, LD12.5∶11.5 to terminate diapause. Chilling temperature and duration had a significant effect on the development of aestivating and hibernating pupae. The durations of diapause for both aestivating and hibernating pupae were significantly shorter when they were exposed to low temperatures of 1, 5 or 10°C for 50 or 60 days, suggesting that the optimum chilling temperatures for diapause development were between 1 and 10°C and the required optimal chilling period was about 50–60 days. Eighty days of chilling was efficient for the completion of both summer and winter diapause. When chilling periods were ≥90 days, the durations of summer and winter diapause were significantly lengthened; however, the adult emergence was more synchronous. The adaptive significance of a similar mechanism on summer and winter diapause development is discussed.暗脉菜粉蝶（Pieris melete）以滞育蛹的形式越冬与越夏。本研究提供证据表明，调控夏季与冬季滞育发育的最佳低温条件及最优低温处理时长，其作用机制具有相似性。我们将夏季或冬季滞育蛹置于1、5、10或15℃的不同低温环境下，分别进行30至120天不等的低温处理，或在滞育的不同阶段启动低温处理，随后将其转移至20℃、光周期LD12.5∶11.5的环境中以解除滞育。低温处理的温度与时长对越夏与越冬滞育蛹的发育均存在显著影响。当滞育蛹经1、5或10℃低温处理50或60天时，越夏与越冬滞育的持续时长均显著缩短，这表明滞育发育的最佳低温处理温度范围为1~10℃，所需最优低温处理时长约为50~60天。80天的低温处理可有效完成夏季与冬季滞育的发育进程。当低温处理时长≥90天时，夏季与冬季滞育的持续时长会显著延长，但成虫羽化的同步性会有所提升。本文还探讨了该相似调控机制在夏季与冬季滞育发育中的适应性意义。