Diapause, a developmental arrest mechanism, helps animals to survive seasonal changes via endocrine regulation. While obligate diapause is genetically programmed, facultative diapause is typically triggered by environmental cues such as photoperiod. In insects, this often leads to reproductive diapause characterized by reduced juvenile hormone (JH) signaling, resulting in ovarian arrest and lipid accumulation. However, the molecular link between photoperiod and hormonal control remains poorly understood. In this study, we investigated the cabbage beetle