they have a sinister purpose. 它们却是阴险的陷阱

15. A silicon strand is lowered from the ceiling,
    一根坚韧的丝从天顶上垂下
16. alongside hundreds of others.
    边上还有好几百根
17. Beautiful though these threads are,
    虽然这些丝看起来很漂亮
18. they have a sinister purpose.
    它们却是阴险的陷阱
19. This is a cave glow worm.
    这是一种洞穴萤火虫
20. To trap its prey it goes fishing with a line of silk.
    它利用一根根的丝来诱捕猎物
21. The silk comes from glands in the glow worm's mouth
    丝产生自萤火虫口中的腺体

来自《行星地球 第一季 第四集 Planet Earth S01E04 洞穴》第 18 行