西花蓟马在黄瓜和架豆上的空间分布型及理论抽样数

西花蓟马Frankliniella occidentalis（Pergande）已在北京部分蔬菜园区成功定居，对蔬菜生产造成危害。为了解该虫在蔬菜田的种群空间分布型，指导田间取样，本文应用几种聚集度指标的计算公式以及Taylor、Iwao的回归方程式，分析和测定了西花蓟马的种群空间分布格局。结果表明：在黄瓜和架豆上西花蓟马的空间分布型一致，均为聚集分布型；该虫的空间分布型不受种群密度的影响，并且也不随取样时间的变化而变化。种群数量动态研究显示西花蓟马成虫和若虫在黄瓜植株的中部叶片分布较多（从顶部向下数第4叶至第17叶片上成、若虫的分布数量多于其他叶片上的数量），未展开的叶片、嫩叶和下部老叶危害较轻。用Iwao回归法中α、β参数计算出在允许误差范围内的理论抽样数。

Spatial distribution pattern and sampling of the western flower thrips,Frankliniella occidentalis (Pergande) (Thysanoptera: Thripidae), on cucumber and green bean

The western flower thrips, Frankliniella occidentalis (Pergande), has successfully settled down in parts of Beijing vegetable production areas and damaged a lot of vegetables. In order to understand the spatial distribution patter of this pest, its population aggregating indexes on cucumber and green bean were calculated based on the related index formulae, and Taylor and Iwao regression formulations. The results showed that the spatial distribution pattern of the western flower thrips belonged to aggregating distribution on cucumber and green bean. Differences in sampling time and population densities had no effect on the spatial distribution pattern of F. occidentalis. Analysis of population dynamics showed that adults and larvae of the thrips mostly were feeding on middle leaves of cucumber (the number of thrips on 4th to 17th leaf was higher than that on other leaves), and that thrips caused lighter damage to unfold leaves, the younger and the older leaves. Theoretical sampling within allowable error by α and β based on Iwao regression formulation was measured.