viral disease had been reported indeclining populations of caterpillars, but populationecologists had usually considered viral disease to have contributed to the decline once it wasunderway rather than to have initiated it.（这个长难句没看懂）
我认为，it代指decline,it was underway指的是毛毛虫群体数量下降这件事情正在发生。rather than后的内容与to have contributed to平行，这句话的意思就是说人口学家常常会认为一旦毛毛虫群体数量下降，是病毒疾病助长了数量不断下降，而不是导致了毛毛虫数量下降。
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发表于 2023-7-24 10:48:36
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