fewer than any other用比较级表示最高级，也就是说今年回来的黑脉金斑蝶数量是最少的。

2.The researchers then purposely interfere with the monarchs and follow their movement again.

interfere with干预, 阻挠, 妨碍, 阻止

例句：That interferes with my plan.
      那干扰了我的计划。

      The noise interferes with my work.
      这噪音妨碍我的工作。