《华盛顿邮报》报道，专家说，主要原因之一是，农民对马利筋植物使用除草剂，而这些蝴蝶以马利筋植物为食。
The Washington Post reported, one of the main reasons, experts say, is that farmers have used herbicides on the milkweed plants that these butterflies feed on.
黑脉金斑蝶的毛虫只吃马利筋的叶子。
Caterpillars of monarch butterflies feed exclusively on milkweed leaves.
马利筋中的特殊糖苷在帝王蝶的范围内因地区而异。
The specific glycosides present in milkweed differ from region to region within the monarch butterfly's range.
在实验中，这些毛毛虫被喂食沾有转基因玉米花粉的马利筋叶子，然后它们死亡了。
When, in experiments, these caterpillars were fed milkweed leaves dusted with pollen from modified maize plants, they died.
一只沙漠蛛蜂正在吞食马利筋的花粉。
有一群这样的马利筋竟然侵入了我们的水边花园。
作为顽强的，屡败屡战的马利筋，它立刻就生发出更多的笋芽，妄图卷土重来。
蝴蝶和马利筋，犹如立足笔尖的铅笔，依靠共同进化的递归动态而立得笔直。
They are held together, poised upright like a pencil standing on its point, by the recursive dynamics of coevolution.
马利筋为自我保护如此认真地抵抗黑脉金斑蝶的侵袭，结果变得与蝴蝶难舍难分。
In defending itself so thoroughly against the monarch, the milkweed became inseparable from the butterfly.
环保署估计，即使马利筋叶片上每平方公分有高达150颗的玉米花粉，昆虫食用后也没有明显的危害。
The EPA estimates that the insects face no observable harm when consuming milkweed leaves laden with up to 150 corn pollen grains per square centimeter of leaf surface.
缓慢的，散发着蜂蜜香味的花朵如礼花般绽放，七月的时候，池塘边的4英尺高的马利筋依稀长成了一堵屏风。
The plants bloomed in slow, honey-fragrant fireworks, and by July there was a 4-foot wall of milkweed screening a dimly remembered pond.
基因作物可以抵抗除草剂，这样农民就可以用除草剂除掉马利筋，而马利筋是黑脉金斑蝶最主要的食物来源。
S. midwest. The gene crops are designed to resist herbicides and that's allowed farmers to wipe out milkweed, which is the main food source for Monarches.
基因作物可以抵抗除草剂，这样农民就可以用除草剂除掉马利筋，而马利筋是黑脉金斑蝶最主要的食物来源。
S. midwest. The gene crops are designed to resist herbicides and that's allowed farmers to wipe out milkweed, which is the main food source for Monarches.
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