Studies On The Spider Community In Cabbage Field And Predation Of Dominant Spiders For Major Insect Pests

This paper is based on the preliminary investigation of spiders in the fields and forests in Shanxi province, it is importantly studied that spider and insect community from, the structure, time niche, space niche, two dimension niche and predatory function of Pardosa astrigera, Erigonidium graminicolwn and Oedothorax feminea to Plutella maculipennis Curtis and Vegetable Aphides in the cabbage field in Taigu. The result will give the certain statement for the protection of natural enemy and sustainable IPM.1. The spider resource was studied among 11 areas in Shanxi, there were 176 species belonged to 19 generas 12 families, the dominant spider was Pardosa astrigera.2. It was preliminarily studied that the spider and insect's community in cabbage field in Taigu and the changes of fluctuation of the dominant species , 29 species belonged to2 classes,8 orders,22 families, at the same time , it was analysed that the degree of richness(S), total individual number(N),index of diversity(H) and degree of evenness(E) about the community and stated that the mechanism of using the spider to control the insect pests in cabbage ecology system .in addition ,it was stated that the important meaning about protecting and using the spider according to the index of dominant degree(D) which was used to analyse time dynamics.3. According to the date from April 20 July 18 in 2004, it was studied that the time niche, space niche and the two_dimensional niche, the overlap value stated that the dominant natural enemies were Pardosa astrigera , Erigonidium graminicolum , Oedothorax feminea to Plutella maculipennis Curtis , Vegetable Aphides.4. It was investigated that the foraging behavior of three predators(X1-Pardosa astrigera , X2-Erigonidium graminicolum, X3-Oedothorax feminea) for two major insect pests in cottage fields(X4-Brevicoryne brassicae, X5-Plutella maculipennis Curtis), as well as how the interference among and within species occurred, by using the rotational composite design of quadratic regression. It is obtained those six models of predatory capacity in the coexistent system of three spiders and two insect pests in cottage fields. One of them was :Y3=45.63636+l .33333X1+1.58333X2-0.41667X3+10.75000X4-1.08333X5-3.38636X12-2.13636X2 2-0.51136X32-4.01136X42+0.48864X52+1.00000X1 X2+0.62500X1X3+3.87500X1X4+1.12500X1 X5-0.7 5000X2X3+4.50000X2X4+2.50000X2X5-3.37500X3X4-2.62500X3X5-0.12500X4X5The principal efficiency analysis on this model indicated that increases in insect pests density had significantly increased the predation of predators on the insect pests and had a greater effect than any one of predators. X₄ had a great effect than X₅. However, X₄ and X₅ had little interference in this experiment densities, they even promoted each other and increased the greatest effect on the increase of predation. X₁ had the second and a little greater than X₂ the third. As the predator density increased the inter and inter-species interference occurred, which were largely related to the size, activity, niche breath, niche overlap and searching efficiency of the predators. X₁ had the greatest interference between different...