中文摘要：

水生甲虫（昆虫纲，鞘翅目）群落结构受多种环境因素的制约．西苕溪中上游流域38个样点共发现水生甲虫12科36个分类单元．优势属是长角泥甲科的Stenelmis属和扁泥甲科的Psephenoides属，出现频度分别为30和22，但有29属的出现频率不大于5．典范对应分析（CCA）表明，鞘翅目群落组成受荫蔽度、总氮、电导率和栖境质量影响最大．样点环境指标聚类结果与CCA结果一致，样点被分为3组．从第1组至第3组，水体中的总氮（2．80—3．52mg／L）和化学需氧量（14．5—20．29mg／L）明显上升，荫蔽度（18—6）明显降低．第1组（18个分类单元）和第3组（16个分类单元）的水生甲虫种类组成差异极显著（P〈0．01），第2组水生甲虫多样性最高（26个分类单元）．Macronychus，Zahze—via，Scirtes，Stenocolus，Berosus，Laccobiuz和Ectopria属可作为清洁水体指示生物，Hydrocassis和Ancyronyx属是重污染水体指示生物．图3表4参16

英文摘要：

36 taxa in 12 families of aquatic beetles were collected from 38 sampling sites in the upper reaches of the Xitiao Stream. Stenelmis and Psephenoides were dominant genera with their occurrence frequencies of 30 and 22 times, respectively, but other 29 genera appeared less than 5 times. Canonical correspondence analysis （CCA） between aquatic beetles and environmental factors showed that canopy was the main factor affecting beetle community distribution, and other factors were total nitrogen （ TN）, water conductivity and habitat quality. The sampling sites were classified into three groups through clustering analysis using 17 environmental factors. From group 1 to group 3 of the sampling sites, TN and chemical oxygen demand （COD） increased from 2. 80 to 3.52 mg/L and 14. 5 to 20. 29 mg/L, respectively, but the canopy decreased from 18 to 6. Aquatic beetle community in group 2 （26 taxa） was found with the highest richness. However, the composition in group 1 （ 18 taxa） and group 3 （16 taxa） was significantly different （P 〈0. 05）. Macronychus, Zaitzevia, Scirtes, Stenocolus, Berosus, Laccobius and Ectopria mainly occurred in clean water, but Hydrocassis and Ancyronyx were found only occurring in heavy polluted water. Fig 3, Tab 4, Ref 16