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害虫和天敌共存于农田生态系中,在自然状态下,它们处于生态平衡的动态中,在不同生态条件下,或当其中某种生态因子发生变更,必然引起天敌数量上的变化。因此,在了解天敌种类及其数量变动规律的基础上,进一步研究引起数量消长的原因,为保护利用提供依据。本文是作者于1979～1982年对许昌烟区烟草害虫天敌研究的第三部分。现报道如下:
Pests and natural enemies co-exist in farmland ecosystems. Under natural conditions, they are in an ecologically balanced dynamic. Under different ecological conditions or when some ecological factor changes, they inevitably cause changes in the numbers of their natural enemies. Therefore, on the basis of knowing the types of natural enemies and the changes of their numbers, this paper further studies the causes of the decline in quantity and provides the basis for protection and utilization. This article is the author of the third part of the research on natural enemies of tobacco pests in Xuchang from 1979 to 1982. Reported as follows now: