The life cycle of the butterfly - Franziska Bauer

翻译人员: Riley WANG 校对人员: Zibo Huang

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In order to become a butterfly,

为了变成蝴蝶， 毛毛虫的身体几乎完全分解，

a caterpillar’s body dissolves almost completely

and is rebuilt from its own juices.

并利用这些液体物质重塑身体。

As inconvenient and even downright dangerous as this process sounds,

虽然这个过程听起来既麻烦又危险， 但它却非常普遍。

it’s actually quite common.

Butterflies are just a few of the 800,000 insect species

有 80 万种昆虫会经历 从幼虫到成虫的完全变态发育，

that transition from larvae to adults through complete metamorphosis.

其中蝶类昆虫只占很小的比例。 这 80 万种昆虫大约占

That’s approximately 85% of insects and 70% of all known animal species.

全部昆虫的 85%， 占所有已知动物种类的70%。

But how exactly does a caterpillar become a butterfly?

但毛毛虫到底是如何变成蝴蝶的呢？

When a caterpillar hatches from an egg,

当毛毛虫从卵中孵化出来，

it has none of a butterfly’s physical traits.

它并不具备任何蝴蝶的身体特征，

It does have groups of cells inside its body called imaginal discs

但它的体内拥有一些细胞， 称为成虫盘。

that will eventually become its butterfly parts.

成虫盘最终 会发育成蝴蝶的身体部分。

For now, these cells remain dormant.

现在，这些细胞处于休眠状态。

Juvenile hormone suppresses their activity,

保幼激素抑制着这些细胞的活动，

and prevents the caterpillar from beginning metamorphosis too early.

避免毛毛虫过早开始变态发育。

Immediately after hatching, the caterpillar begins to feed,

从卵孵化后， 幼虫立刻开始进食，

building up fat until its rigid skin, called a cuticle, becomes too tight.

积累脂肪， 直到坚硬的表皮开始绷紧。

At this point, a hormone called ecdysone triggers the cuticle to shed, or molt.

此时，蜕皮激素开始分泌， 促进表皮脱落。

As the caterpillar grows, it usually molts four times.

在发育过程中， 毛毛虫通常需要蜕皮四次。

Then, when it’s nice and plump,

之后，表皮变得漂亮丰满时，

the caterpillar’s levels of juvenile hormone drop,

毛毛虫体内的保幼激素水平下降，

which triggers it to stop eating and moving.

这会使毛毛虫停止进食和活动。

A final burst of ecdysone

蜕皮激素最后一次分泌

prompts the caterpillar’s cells to begin to self-destruct.

促使毛毛虫的细胞进行自我分解。

Soon, the muscles, fat, and other tissues are almost entirely liquefied,

肌肉，脂肪等组织 很快就会接近完全液化，

though the imaginal discs stay intact and begin to grow.

但成虫盘依然保持完好， 并继续发育。

At the same time, a second skin layer called the pupal cuticle

与此同时，第二层皮肤蛹

forms underneath the first.

会在第一层皮之下形成。

One more molt exposes the hard exterior of the pupa.

再一次的蜕皮使蛹的坚硬外壳裸露。

Besides the imaginal discs, only a few tissues are spared,

在成虫盘周围 只有很少的组织得到保留，

including parts of the respiratory system,

其中包括部分呼吸系统，

the heart,

心脏，

some abdominal muscles,

一些腹部肌肉

and the mushroom bodies of the brain.

和脑蕈形体。

The caterpillar juice then fuels the development of the imaginal discs

幼虫解离形成的液体 为成虫盘的发育提供能量，

into eyes,

使其发育成眼睛，

antennae,

触角，

legs,

腿，

wings,

genitalia,

翅膀，

外生殖器

and other body parts.

以及其他身体部分。

Once its new body is built, the insect molts one last time,

一旦新的身体形成， 会进行最后一次蜕皮，

shedding the pupal cuticle.

即脱掉蛹，

From there, it’s free to fly away a new butterfly.

自此 ，一只新蝴蝶诞生了。

Even after such a dramatic transformation,

即便经历了如此巨大的变化，

the butterfly does retain some memories from its caterpillar days.

蝴蝶依然能够保留 部分毛毛虫时期的记忆。

It’s likely the mushroom bodies of the brain

这很可能是由于脑蕈形体

carry important knowledge from the caterpillar over to the adult butterfly.

将幼虫时期的重要知识 传递给了成年蝴蝶。

How did such an involved developmental process come to be?

为何会有这样的发展过程出现呢？

We don’t know for sure.

我们目前仍不确定。

The leading theory is that the caterpillar is actually a drawn-out version

主流理论认为，毛毛虫实际上 是某个生命阶段的延迟，

of a life stage that takes place inside the egg for some other insects.

而对于其他昆虫， 这个过程通常发生在卵中。

According to this hypothesis, over millions of years,

根据这个猜想， 在数百万年间，

the larvae evolved the ability to eat and live outside the egg.

幼虫进化出了吃掉卵壳 和在卵壳外生存的能力。

Regardless of how complete metamorphosis originated,

不管完全变态发育是如何开始的，

it’s become part of the life cycles of a dizzying number of insect species.

它成了大量昆虫生命循环的一部分。

Still, plenty of species get along perfectly well

对许多物种来说，

更简单的发育过程 才是它们所适应的。

with a simpler developmental process.

What survival advantages might complete metamorphosis provide

完全变态发育对生存有什么好处，

to make up for the added hassle?

才能弥补这种额外的麻烦呢？

For one, it keeps larvae and adults

其一，它使得幼虫和成虫

from competing for the same habitats and food sources.

免于争夺栖息地和食物。

And while the pupa may seem vulnerable,

虽然蛹看上去很脆弱，

this immobile stage can actually be a good way

这种静止的状态可以 很好地帮助幼虫

to pass parts of the year when food is scarce.

渡过食物匮乏的时间。

To us, a butterfly’s metamorphosis might sound as fantastic

对我们来说， 蝴蝶的变态发育

as a phoenix rising from its ashes.

如同凤凰涅槃一般奇妙。

But these transformations are taking place all around us, all the time.

但是这些转化 一直都在我们身边进行着。

From the Hercules beetle

从独角仙

to the honey bee

到蜜蜂，

to the garden ant,

再到蚂蚁，

countless squishy larvae dissolve and emerge

不计其数脆弱的幼虫经过分解

as armored, aerodynamic, and nimble adults.

发育成外表更为坚硬、 呈流线型的敏捷成虫。

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