越冬期不同阶段二点委夜蛾越冬幼虫耐寒性变化

【目的】二点委夜蛾Athetis lepigone (Moschler)是我国夏玉米苗期的新害虫，随着耕作制度的改变，二点委夜蛾的发生危害区域和面积逐渐扩大。本研究探讨二点委夜蛾的抗寒能力，为揭示抗寒机理提供理论基础。【方法】分别在越冬期的3个不同阶段，即越冬初期（2012年11月7日）、越冬期（2012年1月20日）和越冬末期（2013年3月5日），对二点委夜蛾老熟幼虫的体重、过冷却点（supercooling point, SCP）、结冰点（freezing point, FP）、含水量、脂肪和糖原含量进行测定。【结果】过冷却点在这3个时期有显著差异，最低值（-23.16±0.38℃）出现在1月份，最高值（-16.24±1.24℃）出现在越冬初期，结冰点变化趋势与过冷却点一致。通过定量检测发现，虫体鲜重与过冷却点无相关性（r=0.17, P=0.12）；脂肪含量在越冬初期含量最高，而在越冬末期最低；糖原含量在越冬期含量最低；自由水的含量随着过冷却能力升高而降低，随其降低而升高，而结合水含量恰好相反。【结论】二点委夜蛾的抗寒性在越冬期不同阶段出现明显的变化，即随着冬季低温的到来，其抗寒能力逐渐增强，冬季过后又随气温的回升，其抗寒力逐渐减弱。

Changes of cold hardiness of the overwintering larvae of Athetis lepigone (Lepidoptera: Noctuidae) at different overwintering stages

 【Aim】 Athetis lepigone (Moschler) is a new insect pest of summer corn at seedling stage in North China. With the transformation of cultivation, the damage area of A. lepigone has been gradually expanding. In this study, the cold hardness of A. lepigone was measured to reveal its cold resistance mechanisms. 【Methods】 We measured body weight, the supercooling point (SCP), the freezing point (FP) and the contents of water, fat and glycogen in mature larvae at different overwintering stages (the early overwintering stage, November 7th, 2012; the overwintering stage, January, 20th 2012; while the late overwintering stage, March 5th, 2013). 【Results】 The SCP values on different dates during overwintering were significantly different, the lowest SCP value (-23.16±0.38℃) appeared in January, while the highest (-16.24±1.24℃) appeared at the beginning of winter. The variation tendency of FP value was consistent with that of SCP. According to the quantitative detection, we found that the fresh body weight had no correlation with SCP (r=0.17, P=0.12). The highest fat content appeared at the beginning of winter, while the lowest appeared at the late overwintering stage. The lowest glycogen content appeared at the overwintering stage. Supercooling capability enhanced as the free water content decreased, while reduced as the free water content increased. However, the change of bound water content was opposite to that of the free water content. 【Conclusion】 The cold hardiness of overwintering larvae of A. lepigone changes significantly at different overwintering stages, which gradually strengthens as temperature decreases in winter and weakens as temperature increases after overwintering.