| This paper studied the ecology of Oligonychus perditus population on the Platycladus orientalis forest. The main contents and conclusions are as follows:1. The developmental durations of different stages of Oligonychus perditus were studied under constant temperatures. The developmental temperature and effective thermal summation of different developmental stages and one generation of 0. perditus were worked out by the linear regression equation and LiDian-mo"s optional methods. It could be forecasted that 11 or 12 generations may occur in MT. Tai Shan, Shan Dong Province based on the effective thermal principle, which is in conformity with the actual occurrence. This experiment was firstly studied under constant temperatures at home and abroad.2. The life table of Oligonychus perditus population was studied at the constant temperature 25?. 5癈 and relative humidity 70%~80% in laboratory. The result were as follows, the intrinsic increase rate (r.) was 0.1274, the finite increase rate (A.)was 1.1358 per day, the net reproductive rate (R,)was 20. 0586 per generation,the mean generation time (t) was 5.4407 days. In aged distribution of constant population, the percentage of the immature period was 91. 1586% and that of the mature period was 9. 3716%. The instantaneous birthratewas 0.1651, and the instantaneous death rate was 0. 0377.3. The spatial distribution pattern of over-wintering eggs of Oligonychusperditus on Platycladus orientalis forest of MT. Tai Shan were measured by means of several indexes of aggregation and regression methods. The results manifested that over-wintering eggs on leaves in different directions, sampling plots and sampling land obey aggregation distribution which was resulted in by egg-laying characteristic of 0. perditus adult, and not non-environmental factors. The spatial distribution of 0. perditus over-wintering eggs is closely related to the number and characteristic of 0. perditus aggregation and dispersion.4. In laboratory, the predaceous roles of Conwentzia sinaca Yang, Erigonidium graminicoJwn(Sundevall) , Scolothrips takahashia Priesner and Aeolothrip fasciatus(Linnaeus) were studied .The results indicated that alltheir functional responses to 0. perditus belonged to Moiling II type. The predator density and size, the length of being starved and the size of habitat, prey type and density, and all many other factors could affect the predation of natural enemies variously under different conditions.5. Fifteen species of pests and thirty-four natural enemies were collected and obtained from the southern Platycladus orientalis forestry of MT. Tai Shan , which belong to forty families, ten orders, and two classes, including fourteen natural enemies of Oligonychus perditus . 0. perditus population dominated the insect and natural enemy community with higher dominance than the other insects. The dominance of Oliginychus perditus and its predators varies with the lapse of time.Population dynamic of 0. perditus was related closely with the environmental factors, which were affected by temperature, relative humidity, rainfall, natural enemies and other disastrous conditions. The efficiency of the natural enemies of 0. perditus was valued by Relation theory of Grey System. The relation between each environmental factor and 0. perditus population was analyzed by the Relation Coefficient method. The results indicated that the population dynamic of 0. perditus was negatively correlated with rainfall, raining frequency and relative humidity, but positively with temperature and natural enemies.The spatial and temporal niches and the two-dimensional niches of major Other pests, Oliginychus perditus and natural enemies in the Platycladus orientionalis forestry were studied. The results manifested that the one-dimensional spatial niches of them in temporal sequence were dynamic. Their niches breadth expanded or contracted with the lapse of time. The niche of natural enemies followed that of the pests, and in turn, it resulted in the shrink of the niches of the p...
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