Populations of purple milkweed butterflies one of 400 butterfly species on the island and once sold to black market dealers for its worth as a collectors 'item have rebounded thanks to the rerouting of expressway trucks that cut across their ancestral migratory paths. 这里的紫斑蝶是台湾岛的400种蝴蝶之一,因其收藏价值曾被卖往黑市。高速公路曾切断它们古老的迁徙路线,高速路改道后,这种蝴蝶的数量开始回升。