在河北省大兴县除虫工作中,我们结合群众经验,本着就地取材的方针,创造了些防治棉蚜及火蜘蛛的土法,这些土法,在防治效果上讲,一般均在百分之五十至百分之七十 In the work of exterminating Daxing County in Hebei Province, we combined with the experience of the masses and based on the principle of obtaining materials on the spot, we have created some indigenous methods of controlling cotton aphids and fire spiders. These indigenous methods are generally effective Fifty to seventy percent