Abstract: 【Aim】 This study aims to ascertain the difference in the contents of biochemical substances and protective enzyme activities between the diapausing and non-diapausing larvae of Leguminivora glycinivorella so as to provide a basis for further exploring the molecular mechanism of diapause regulation. 【Methods】 The diapausing and non-diapausing larvae of L. glycinivorella were obtained by controlling the photoperiod conditions at a suitable temperature (25℃). The supercooling point, the freezing point, the contents of main biochemical substances including carbohydrate, lipid substance and soluble protein, and the activities of protective enzymes including peroxidase (POD), catalase (CAT) and superoxide dismutase (SOD) beween the diapausing and non-diapausing larvae were assayed and compared. 【Results】 At 25℃, the supercooling point (-19.20℃) and the freezing point (-13.49℃) of the diapausing larvae of L. glycinivorella were lower than those of the non-diapausing larvae (-16.42℃ and -11.22℃, respectively), suggesting significant difference in the supercooling capacity between both. The contents of total sugar, glycerin, glycogen and other energy substances in the diapausing larvae were significantly higher than those in the non-diapausing larvae. The total sugar content and the glycerol content in the diapausing larvae were 2.17 and 1.76 times as high as those in the non-diapausing larvae, respectively. However, there was no significant difference in free water and soluble protein contents between the diapausing and non-diapausing larvae. At the same time, the POD and CAT activities in the diapausing larvae were significantly higher than those in the non-diapausing larvae, while the SOD activity in the diapausing larvae was slightly lower than that in the non-diapausing larvae, but there was no significant difference between both. 【Conclusion】 During the process of L. glycinivorella larvae entering diapause state from non-diapause, the contents of biochemical substances like carbohydrates are significantly increased, and the activities of some protective enzymes are significantly enhanced by the regulation of physiological metabolism, which in turn significantly improves their supercooling capacity to effectively cope with adverse environmental conditions like low temperature.

Key words: Leguminivora glycinivorella, diapause, supercooling point, protective enzymes, environmental suitability