原文视听

But the milkweed has a defence mechanism.
不过马利筋也有对策
As the caterpillar bites into a vein,
毛虫只要咬破叶脉
a kind of latex swells out engulfing it.
叶子就会流出一种胶乳包住毛虫
If the caterpillar isn't quick, it will drown...
如果毛虫动作太慢就会淹死
or find its jaws glued together.
或是被黏得张不开嘴
The plants' defence is so effective
马利筋的防御机制相当有效
that only one third of the Monarch caterpillars make it through the first day.
只有三分之一的毛虫 能撑过第一天
But the caterpillars that survive, grow in size and strength.
大难不死的毛虫 体型和力气与日俱增
And they go for the jugular.
然后开始攻击马利筋的要害
By carefully chewing through the main vein,
它们小心地咬破主脉
the caterpillar drains the leaf of latex
让叶片的胶乳流干
and cuts off its supply.
并阻断其供应
The milkweed's leaf is now defenceless
这下马利筋的叶片 再也无力反击
and the caterpillar eats in safety before preparing to pupate into a butterfly.
毛虫可以放心大嚼，然后成蛹化蝶

重点解释

As the caterpillar bites into a vein,a kind of latex swells out engulfing it.毛虫只要咬破叶脉叶子就会流出一种胶乳包住毛虫

bite into咬入；腐蚀

The little girl's tooth came out when she bit into the apple.

这小女孩在咬苹果时，她的牙掉了。

This piece of meat is very tough, and no one has been able to bite into it.

这块肉很硬，谁也咬不动。

the caterpillar drains the leaf of latex and cuts off its supply.让叶片的胶乳流干并阻断其供应

cut off切断

He cut off a bunch of grapes to entertain us.

他剪下一串葡萄招待我们。

A storm that cut off power to the whole region.

切断了整个地区电力供应的暴风雨

the caterpillar eats in safety before preparing to pupate into a butterfly.毛虫可以放心大嚼，然后成蛹化蝶

prepare to准备

We are not prepare to consign the goods.

我们不准备寄售此货。

Are you prepared to submit to my decision?

他准备对我的决定让步吗？