英语听力文摘 English Digest 369、“勒不死”的苍蝇（在线收听）

Can You Choke a Fly?
你绝对勒不死苍蝇

Don:These dark flies are driving me badly! I wish I could strangle each of every one of them!

Yaël:I’m sorry to say, but that’s impossible.

D: I realize that. I don’t mean that I have to strangle all of them. Really, I did happy if I could strangle even just one or two of them.

Y: Impossible!

D: I’m sure. I can just manage to just strangle one if I had some dental flosses or something.

Y: I’m sure you couldn’t because insects breathe quite differently from us. They don’t have a central area like our lungs where they gather oxygen; nor a transport system like our heart, and the blood used to deliver oxygen to all of our cells.

Nope. Flies, like all insects, breathe through many tiny openings called spiracles. These openings are part of tubes called trachea. Each tube leads to a fluid-filled tracheole, where the oxygendissolves and then diffuses across the wall of the tracheole and into several of the insect’s cells. So there is no central breathing area to block off so that you might strangle a fly.

However, if you wanted to drown a fly, that’s another story. The spiracles of most insects can close to keep things like dust out. Therefore, they can hold their breath, so to speak. But if an insect is trapped in water for too long, it will run out of oxygen and eventually drown.

D: Now, I just have to figure out how to lure them all into some water.

Don: 这些飞来飞去的黑苍蝇快把我逼疯了！我真想把他们全部勒死！

Yaël: 很遗憾，你办不到！

D:我知道，要全部都勒死不容易，不过，哪怕勒死那么一两只也好啊！

Y:你还是办不到！

D:我保证如果有类似牙线的东西，我肯定能勒死一只苍蝇。

Y:我打赌你做不到。因为昆虫呼吸可不像我们人类的。昆虫既没有肺似的中心区域，可以容纳空气；也没有像心脏似的运输系统，可以通过血液循环，给身体所有细胞供氧。

苍蝇，和所有昆虫一样，通过无数微小的气门来进行呼吸。气门是气管的部分。气管又分支成许多微气管，微气管里充满液体，吸入的氧气溶解于其中，穿透气管管壁扩散到昆虫的无数细胞中。所以， 你没方法让苍蝇窒息。

但是，如果你想让苍蝇淹死，又是另外回事了。大多数昆虫紧密气门，防止灰尘进入。这样，它们不得不屏住呼吸，但是如果在水里太长时间，它们会因为缺氧而溺死。

D:那么，现在我只要想法子让苍蝇掉进水里就可以啦！

diffuse:扩散，弥漫

cell: 细胞