| The predacious mite Euseius castaneau is one of the biological control agents of Phytoseiidae in China which has not been studied before. We discovered it has some potential control effect on the Frankliniella occidentalis by some laboratory experiments. It is necessary to study its biology and experimental population ecology. In this thesis, the biology characteristics were observed and some experiments which are related to predation abilities to the Frankliniella occidentalis were carried out both under the laboratory conditions and field surveys. Furthermore, the influence of nine kinds of pollen and two-spotted spider mite on immature development and reproduction of Euseius castaneau was also researched. The results are as follows.1. E. castaneau conducts bisexual reproduction. The life span experiences five stages: egg, larva, protonymph, deutonymph and adult. It can prey spider mite, thrips and eggs of storage pests. When lacking of food, the adult can feed the larvae and nymphs of the species. The adult females can mate repeatedly, and prefer ovipositing on the cellosilk of cotton. The adults overwinter in the needle dry weeds, dry tree bark and leaves of chestnut trees in the chestnut orchard.2. The functional response for adults of N. cucumeris and E. castaneau could be described by the HollingⅡfunctional response type: The functional response equation could be expressed as Na=0.763×Nt/(1+0.152Nt) for N. cucumeris and Na=0.257×Nt/(1+0.032Nt) for E. castaneau, respectively. The attack rates and the handling times Th for N. cucumeris and E. castaneau were 0.763 and 0.257, 0.199 and 0.125d, respectively. The daily maximum predation rate is 5.020 for N. cucumeris and 8.031 for E. castaneau, respectively. Due to its high predation capacity, E. castaneau should become one of the potential biological control agents of western flower thrips.3. The relationship between the consumption of prey and prey densities followed HollingⅡmode, which could be expressed as Na=0.389×Nt/(1+0.06Nt), and the relationship between oviposition of predatory mite and prey densities could be expressed as y = 0.2309Ln(x) + 0.0133. The numerical response pertained to positive density reaction.4. The starved predatory mite had no preference between thrips and spider mites in the presence of their equal densities, ie. 10:10. It meant the predation is random. (preference index ?1:0.55±0.05), consuming 2.3 thrips and 1.9 spider mites, during the experimental periods of 24 h. When the density ratios of thrips to spider mites were 1:1-1:4, the predatory mite had also showed no preference. However, as the density ratio increased to 1:5, the predatory mite showed a clear preference for spider mite (preference index ?1: 0.29±0.09). Predation on spider mites increased when their ratio to thrips increased, but the disproportionate predation (i.e., the functional response) of E. castaneau towards spider mites resulted in a linear increase in the preference for F. occidentalis.5. E. castaneau could complete its immature stages when supplied each of nine kinds of pollen(Tea, lotus, corn, astragalus, schisandra, ginkgo, pine, rose, rape pollen)and spider mite. However,development time from egg to adult varied from 146 to 174 hours for male and from 156 to 191 hours for female. When spider mites were supplied as food, the developmental duration of the male and female of the predatory mite were 160h and 151h,respectively,which showed no significant difference with tea, corn and pine pollen as food, but showed significantly shorter developmental duration than the other pollen as food. The developmental duration of Euseius castaneau for the male was shorter than that of female when fed with the same diet. Female longevity varied from 5.4 to 19.1 days,while fecundity ranged from 0.6 to 5.1 eggs/female. When tea, corn and spider mite were supplied as food, the fecundity of E. castaneau was 3.9, 4.3 and 5.1 eggs/female, respectively, significantly higher than other supplied foods for the test, and also oviposition period, oviposition late period and longevity were significantly increased when the three food resource above supplied.
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