【摘要】 <正> 关于天敌对猎物选择捕食作用的表述和测度,前人曾提出过不少方法或公式。例如Murdoch（1969）以如下形式定义了捕食者对猎物的选择:Na₁/Na₂=C₁N₁/N₂其中 C₁为选择参数,Na₁和 Na₂ 为捕食者捕食两种不同猎物的数量,N₁和 N₂为两种不同猎物的数量。C₁>1说明捕食者选择的是 N₁;C₁<1说明选择的是 N₂;C₁=1说明对两种猎物的喜好程度一致。他还提出了 C₁的三种估计方法。此公式虽能表明捕食者对两种猎物的选择,但不能直接估计选择系数,尚需进一步变换和演算。更多还原

【Abstract】 Many methods and formula to express and evaluate the selective predation ofnatural enemies on their preys have been possed by different authers,but fewof them are adapted to the situation of coexistence of one predator with morethan one species of preys.A new formula therefore is put forward in thepresent paper.Ci=Nai/∑Nai÷Ni/∑Ni=Nai/∑Nai·∑Ni/NiCi:selective coefficient to one prey i.Ni:number of one prey i.∑Ni:total number of prey i. Nai:captured number of one preyi.∑Nai:total captured number of preyi.This new formula was checked with practical data and the results were asfollow:When Erigonidinm graminicola,a predatory spider,coexist with cottonaphids,Aphis gossyppi and eggs of cotton boll worm,Heliothis armigera,C₁（aphids）=1.1428,C₂（eggs of boll worm）=0.8562.When this spider coexist withcotton aphids,eggs and 1st instar-larvae of cotton boll worm,C₁（aphids）=0.6780,C₂（eggs of boll worm）=0,C₃（Iarvae of boll worm）=2.5001.The results showedthat this new method is feasible,but further examinations and Amendments alsoare needed.更多还原