蜀柏毒蛾种群生物学指标的研究

A Study of Biological Indexes of Parocneria orienta Population

根据1990～1992年观测试验,蜀柏毒蛾1年发生2代,第1代自然种群的发育历期平均116天,第2代以卵或初龄幼虫越冬,又称越冬代,平均发育历期249天。蜀柏毒蛾种群的年龄结构是不断变化的,越冬时期的结构也是如此。在食物充分时,雌性比稍低于雄性比;食物匮乏时,雌性比下降;雄性种群的发育稍先于雌性种群。越冬代雌成虫生殖力(平均产卵量)264粒,第1代生殖力124粒。蜀柏毒蛾的繁殖速度R=7695,实际情况下,R值要小得多,甚至小于1;因为各代各期都有死亡发生,抽样调查表明各时期死亡率从百分之零点几至几十不等;固定标准地连续调查表明大暴发前林间自然种群累积死亡率=95.35％,种群数量消长指数I=1.82,而大暴发后累积死亡率=99.49％,I=0.31。蜀柏毒蛾幼虫会因风或食物欠缺而被迫迁移,但迁移距离很短;而成虫则主动迁飞扩散。两代幼虫皆为6龄,各龄头宽体长的对数值皆依龄数呈直线增长。本文还介绍了该虫幼虫取食量,排粪量,成虫产卵历期,卵块平均卵粒数等重要生物学数据。

According to the observations and experiments from the year 1990 to 1992 it is found that Parocneria orienta produces the two generations in a year. The development phase of the first generation population lasts 116 days on an average. The second generation winters in the form of eggs or first instar larvae, thus named the wintering generation, having an average development phase of 249 days. The age structure of Parocneria orienta changes continuously,and so does that in its wintering phase. When food is full,its female ratio will be slightly higher than its male ratio. When food is lacking,its female ratio will decrease. Its male population develops a little earlier than its female population does. The wintering-generation female adults generate 264 eggs, on an average, while the first generation female adults do 124 eggs. The propagative rate (R) of parocneria orienta is equal to7695. But in practical case,R is much smaller,even less than 1. Death will fall on its two genera tions in its various phases. From sampling investigations it is found that the death rates in various phases will vary from less than 1 to tens percent. For example,in accordance with continued investigations on fixed plots, before a great occurrence the cumualative death rate of its natural population in forest is 95. 35%, and the growth and decline index (I) of its population quanuty is equal to 1. 82. But after a great occurrence,the cumulative death rate is 99. 49% and I is 6. 31. The larvae of parocneria orienla have to migrate by the wind or because of deficient food,and have a short mov ing distance. And yet the adults will be active to migrate. All the larvae of the two generations will have six instar classes,and the logarithmic values of every instar larvae in the width of their heads and the length of their bodies will increase linearly with instar classes. In addition, this paper de scribes other important biological bases such as food and defecation quantity of larvae and egg gener ating period of adults.