Composition and structures of insect community of the alfalfa pasture in theLongdong Loess Plateau

A field survey was conducted to determine the composition and structures of insect community of alfalfa pasture in the Longdong loess plateau of. This study showed that the total number of insects was 21021, and they were subordinated to 12 orders, 69 families and 115 species, in which the species were the most from Coleoptera, Lepidoptera and Hymenoptera families, and the individual number of Homoptera, Coleoptera, Hemiptera and Diptera were the biggest. The dominant species were Acyrthosiphon pisum, Sitona lineatus and Adelphocoris lineolatus. The pest, the natural redator, the neutral insects and beneficial insects accounted for 67.54%, 19.79%, 11.20% and 1.47%, respectively.