To clarify the role of waterfront vegetation of floodplains for adult aquatic insects, Trichoptera and Diptera (Tipulidae and Chironomidae), in the middle reaches of the Chikuma River from May to July, an investigatio...To clarify the role of waterfront vegetation of floodplains for adult aquatic insects, Trichoptera and Diptera (Tipulidae and Chironomidae), in the middle reaches of the Chikuma River from May to July, an investigation of the number of these insects was conducted by trapping in each type of vegetation using board traps.A total of 2608.5 adults/m 2 were collected, and we identified a total of 26 species belonging to three taxa,i.e., seven species of Trichoptera, four species of Tipulidae and 15 species of Chironomidae. The most abundant species was Psychomyia acutipennis in Trichoptera (95.7%). There was a significant difference between the number of P.acutipennis in the all vegetation area (especially, Salix subfragilis) and the control area (no vegetation) during the investigation periods (P<0.05, Mann-Whitney U-test). Other taxa did not show a significant difference between the all vegetation area and the control. Moreover, the numbers of adult P. acutipennis showed a significant difference in height on each vegetation. In the case of Vicia villosa varia and V. villosa varia plus dead Phragmites australis, the highest number was caught in the traps set in the boundary between one plant and the plant above (P<0.05, Steel-Dwass Test) in May.On the other hand, in the case of almost all vegetation during the investigation periods (except of S.subfragilis in May, Melilotus officinalis plus dead P.australis in June), the highest number was caught in the traps set up within the vegetation (P<0.05, Steel-Dwass Test).As a result, a significant difference was observed in the number of trapped P.acutipennis according to the vegetation and its height.It is suggested that the existence of multiple types of vegetation in the floodplain plays an important role for maintaining the diversity of the fauna there.展开更多
The prey-seeking behavior of three spiders (X1-Pirata subpiraticus, X2-Clubiona japonicola and X3-Tetragnatha japonica) for brown plant hopper (X4-Nilaparvata lugens) and rice spittle bug (X5-Cal-litettix versicolor) ...The prey-seeking behavior of three spiders (X1-Pirata subpiraticus, X2-Clubiona japonicola and X3-Tetragnatha japonica) for brown plant hopper (X4-Nilaparvata lugens) and rice spittle bug (X5-Cal-litettix versicolor) was investigated, as well as how interference between and within species occurred, by using a quadratic regression rotational composite design. Six predation models derived from the analysis of interactions among and within predators and preys were developed. The total predatory capacity of spiders on rice insect pests after coexistence for one day can be expressed as follows: Y3 = 32.795 + 2.25X1 + 1.083X2 + 0.5X3 + 10.167X4 + 3.167X5 - 1.67X12 - 2.42X22 - 3.295X32 - 0.045X42 + 0.455X52 - 3.125X1X2 + 0.375X1X3 -0.625X1X4 - 0.375X1X5 + 0.375X2X3 - 0.875X2X4 + 0.125X2X5 + 0.375X3X4 - 0.375X3X5 + 0.125X4X5. The principal efficiency analysis using this model indicated that increases in insect pest density significantly increased predation by predators; this was much greater than the effect of any single predator. X4 had a greater effect than X5; however, X4 and X5 demonstrated little interspecific interference and even promoted each other and increased predation rates as the densities of the two pests increased. Among the three predators, an increase in the density of X, had the greatest effect on the increase in predation, X3 had the second, X2 the third greatest effect. As predator density increased inter- and intra-species interference occurred, which were largely related to the size, activity, niche breadth, niche overlap and searching efficiency of the predators. X2 produced the greatest interference between different individuals and between any other predator species. X3 had the second greatest, which reduced predation levels at high predator densities. Because of these factors, the highest predation rate was obtained at a prey density of 120 per 4 rice-hills. The optimal proportion of the three predators in the multi-predator prey system was X1: X2: X3 = 5.6:1.3:4.1.展开更多
基金the River Environment Fundin charge of the Foundation of River Watershed Environment Management ,Japan and Grant-in-Aid for 21st Century COE Programbythe Ministry of Education,Culture ,Sports ,Science ,and Technology.
文摘To clarify the role of waterfront vegetation of floodplains for adult aquatic insects, Trichoptera and Diptera (Tipulidae and Chironomidae), in the middle reaches of the Chikuma River from May to July, an investigation of the number of these insects was conducted by trapping in each type of vegetation using board traps.A total of 2608.5 adults/m 2 were collected, and we identified a total of 26 species belonging to three taxa,i.e., seven species of Trichoptera, four species of Tipulidae and 15 species of Chironomidae. The most abundant species was Psychomyia acutipennis in Trichoptera (95.7%). There was a significant difference between the number of P.acutipennis in the all vegetation area (especially, Salix subfragilis) and the control area (no vegetation) during the investigation periods (P<0.05, Mann-Whitney U-test). Other taxa did not show a significant difference between the all vegetation area and the control. Moreover, the numbers of adult P. acutipennis showed a significant difference in height on each vegetation. In the case of Vicia villosa varia and V. villosa varia plus dead Phragmites australis, the highest number was caught in the traps set in the boundary between one plant and the plant above (P<0.05, Steel-Dwass Test) in May.On the other hand, in the case of almost all vegetation during the investigation periods (except of S.subfragilis in May, Melilotus officinalis plus dead P.australis in June), the highest number was caught in the traps set up within the vegetation (P<0.05, Steel-Dwass Test).As a result, a significant difference was observed in the number of trapped P.acutipennis according to the vegetation and its height.It is suggested that the existence of multiple types of vegetation in the floodplain plays an important role for maintaining the diversity of the fauna there.
文摘The prey-seeking behavior of three spiders (X1-Pirata subpiraticus, X2-Clubiona japonicola and X3-Tetragnatha japonica) for brown plant hopper (X4-Nilaparvata lugens) and rice spittle bug (X5-Cal-litettix versicolor) was investigated, as well as how interference between and within species occurred, by using a quadratic regression rotational composite design. Six predation models derived from the analysis of interactions among and within predators and preys were developed. The total predatory capacity of spiders on rice insect pests after coexistence for one day can be expressed as follows: Y3 = 32.795 + 2.25X1 + 1.083X2 + 0.5X3 + 10.167X4 + 3.167X5 - 1.67X12 - 2.42X22 - 3.295X32 - 0.045X42 + 0.455X52 - 3.125X1X2 + 0.375X1X3 -0.625X1X4 - 0.375X1X5 + 0.375X2X3 - 0.875X2X4 + 0.125X2X5 + 0.375X3X4 - 0.375X3X5 + 0.125X4X5. The principal efficiency analysis using this model indicated that increases in insect pest density significantly increased predation by predators; this was much greater than the effect of any single predator. X4 had a greater effect than X5; however, X4 and X5 demonstrated little interspecific interference and even promoted each other and increased predation rates as the densities of the two pests increased. Among the three predators, an increase in the density of X, had the greatest effect on the increase in predation, X3 had the second, X2 the third greatest effect. As predator density increased inter- and intra-species interference occurred, which were largely related to the size, activity, niche breadth, niche overlap and searching efficiency of the predators. X2 produced the greatest interference between different individuals and between any other predator species. X3 had the second greatest, which reduced predation levels at high predator densities. Because of these factors, the highest predation rate was obtained at a prey density of 120 per 4 rice-hills. The optimal proportion of the three predators in the multi-predator prey system was X1: X2: X3 = 5.6:1.3:4.1.
