spiders are common in daily human experience because of their biodiversity, wide distribution and abundance in favorable seasons. it is unjustifiable that their significance was previouslyoverlooked in biological study. in western countries where arachnology was initiated more thana century earlier than in china, spiders used to be neglected in academic circle. in china, withthe exception of relevant papers published by professor c. ping and professor fen-chen wangseveral decades ago, arachnology remained a vacant field for a long period of time. in recentyears, 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 thisfield.
spiders prey essentially on insects for subsistence. emerged about four hundred millionyears ago and developed along the long evolutionary course of insects, the ancestral spiderspecies 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 improvedmarkedly 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 immensestrength 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. asan 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 valuablein 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 thantwo thousand years in the beginning of han dynasty, spiders were regarded as an augury ofgood 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 southsovereighty, in his book entitled"annotation of west capital"as well as by chen yuan-long inqing dynasty in his writing on"reflection of knowledge from nature". therefore, it could beseen 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 revealedthat 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 ofspiders amounted to 450 000- 3 150 000 per ha. in hunan province, their density in alfalfafields 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 totalweightof "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 couldpositively affirm the immense capacity of spiders in destroying insect pests.
the senior author of this book devoted himself in the study of taxonomy and biology ofcrustaceans and leeches in his early years. since late 1970's he turned to study spiders becauseof the need of biological control of insect pests in agriculture and forestry. during this period hepublished two books and some 180 papers in relation to spiders. he visited five key museums ingermany, france and the united states, and examined type specimens and closely relatedspecies of chinese spiders. he found many species were identified as synonyms; and based onhis own research he gathered additional latest data including newly established taxa. it seemsobviously necessary to systematize and clarify the several hundred chinese spider speciesrecorded by westerners since 1798 and a thousand and more spiders species described by chinese in the recent two decades. his collaborators include a middle-aged professor who hasworked on spiders for years with remarkable achievements, and a young doctor who has completed his dissertation on systematics of wolf spiders and is ready to study other spider taxa.
|
内容加载中，请稍后...
商品评论（0条）