马尾松毛虫幼虫低密度种群空间分布型与落粪分布的研究

虫情监测是森林害虫综合治理的前提。直接观测虫情,常因树木高大而难以实现。对我国林业大害虫马尾松毛虫(Dendrolimus punctatus),已有较理想的模型,通过对林间落粪的调查来估计幼虫数。由于低密度虫情监测尤为困难,而用落粪作间接观测的价值就随之增加,林间一定时段内的落粪是幼虫种群在该时段内活动的结果,其分布则是该时段内种群分布的综合反映。可以设想,落粪分布与种群分布间存在一定关系。对落粪的调查取样,应建立在了解其分布特征的基础上。为此,研究了低密度幼虫种群的空间分布型及落粪分布的规律。

A STUDY ON THE SPATIAL DISTRIBUTION PATTERN OF LARVAE FRASS-DROP OF DENDROLIMUS PUNCTATUS AT LOW DENSITY POPULATION

Frass-drop and characteristics of spatial distribution patterns of the larvae of Dendrolimus punctatus in low population were studied by means of Frequency Distribution, Iwao's and Taylor's method, and some other aggregation indices. The result shows that:(1) The spatial distribution pattern of the overwintering larvae was aggregated, and the basic components of the distribution were single individuals which repel each other, and that of the frass-drop in the same generation tended to be uniform.(2) In the second generation, both larvae and the frass-drop were spatially aggregated, and the degrees of aggregation were higher than that of the overwintering generation. The experimental data were transformed seperately with three methods, among which the Iwao's method is the best for frass-drop data.