Spiders are common in daily human experience because of their biodiversity, wide distribu tion and abundance in favorable seasons. It is unjustifiable that their significance was previously overlooked in biological study. In western countries where Arachnology was initiated more than a century earlier than in China, spiders used to be neglected in academic circle. In China, with the exception of relevant papers published by Professor C. Ping and Professor Fen-chen Wang several decades ago, arachnology remained a vacant field for a long period of time. In recent years, owing to increasing need of biological control of insect pests in agriculture and forestry,attention has been directed to spiders with researchers gradually devoting their studies in this field. Spiders prey essentially on insects for subsistence. Emerged about four hundred million years ago and developed along the long evolutionary course of insects, the ancestral spider species were terrestrial cave dwellers and sluggish in movements. With changes in natural envi-ronment and evolution of insects in their capacity of jumping and flying, spiders improved markedly their ability in jumping and web spinning. They then developed to so-called'true spi ders'(Araneomorphae)in coincidence as insect predators. They are very specialized in possession of complicated spinnerets and well-developed silk glands secreting silk with immense strength and elasticity. Spider silk is extraordinary in its numerous functions in pray catching,locomotion, dispersal and reproduction which are marchless in other animals. Spiders are also unique in changing pedipalps into palpal organs and in their special mode of sperm transfer. As an arthropodian order it contains 35 000 species, uniformly as predators, thus forming a rare phenomenon in the phylogenesis of animal kingdom. Aside from their academic significance in zoological researches, spiders are highly valuable in human productive activities as natural enemies of many agricultural and forest insect pests.In China the beneficial contributes of spiders were recognized early in ancient times. More than two thousand years in the beginning of Han Dynasty, spiders were regarded as an augury of good harvest. There was an old popular saying that aggregation of spiders would bring forth good luck,which was recorded by Wu Jun, a scholar in Liang Dynasty in the period of South Sovereighty, in his book entitled'Annotation of West Capital'as well as by Chen Yuan-long in Qing Dynasty in his writing on'Reflection of Knowledge from Nature'. Therefore, it could be seen that our ancestors highly appreciated the beneficial effects of spiders in agriculture. Investigation conducted by scientific workers in plant protection in past ten years and more revealed that spiders accounted for over 50 % of the total predatory natural enemies of insects in farming areas, while in the rice fields where insecticide application was not too heavy, the population of spiders amounted to 450 000- 3 150 000 per ha. In Hunan Province, their density in alfalfa fields reached as high as 12 750 000 per hectare. An English scholar reported that spider population in South England grassland reached 2 265 000 per acre. It was estimated that the total weight of 'insects destroyed by spiders in England in one year surpassed that of human population in that country. Though it is hardly possible to verify the truth of this statement, we could positively affirm the immense capacity of spiders in destroying insect pests.