The life cycle of the butterfly - Franziska Bauer

譯者: Lilian Chiu 審譯者: Helen Chang

In order to become a butterfly,

為了變成一隻蝴蝶，

a caterpillar’s body dissolves almost completely

毛毛蟲的身體幾乎會完全溶解，

and is rebuilt from its own juices.

然後從自己的體液中重建。

As inconvenient and even downright dangerous as this process sounds,

這個過程聽起來很不方便， 甚至非常危險，

it’s actually quite common.

實際上卻很常見。

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

有八十萬種昆蟲要透過完全變態，

that transition from larvae to adults through complete metamorphosis.

才能從幼蟲發育為成蟲， 蝴蝶只是其中的幾種而已。

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

這類昆蟲約佔所有昆蟲的 85%，

佔所有已知動物物種的 70%。

But how exactly does a caterpillar become a butterfly?

但毛毛蟲到底是 如何變成蝴蝶的呢？

When a caterpillar hatches from an egg,

當幼蟲從蛋裡孵化出來時，

it has none of a butterfly’s physical traits.

牠並沒有任何蝴蝶的身體特徵。

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

牠的體內有一些細胞群， 稱為「成蟲原基」，

that will eventually become its butterfly parts.

最終變成蝴蝶的某些部分。

For now, these cells remain dormant.

目前，這些細胞仍處於休眠狀態。

Juvenile hormone suppresses their activity,

青春激素會抑制它們的活性，

and prevents the caterpillar from beginning metamorphosis too early.

並防止幼蟲太早開始其變態過程。

Immediately after hatching, the caterpillar begins to feed,

孵化以後，幼蟲馬上會開始進食，

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

積累脂肪，直到牠的僵硬表皮， 也就是角質層，變得太緊為止。

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

這時，一種稱為「蛻皮素」的激素 會觸發角質層脫落或蛻皮。

As the caterpillar grows, it usually molts four times.

在成長過程中， 幼蟲通常會蛻皮四次。

Then, when it’s nice and plump,

當幼蟲變得胖嘟嘟時，

the caterpillar’s levels of juvenile hormone drop,

牠的青春激素就會降低，

which triggers it to stop eating and moving.

就會使牠停止進食和移動。

A final burst of ecdysone

蛻皮素的最終大釋放，

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

促使幼蟲的細胞開始自行解離。

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

沒多久，肌肉、脂肪，和其它組織 就會幾乎完全被液化，

though the imaginal discs stay intact and begin to grow.

但是成蟲原基保持完好， 並且開始成長。

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

同時，第二層皮，也就是蛹角質層，

forms underneath the first.

會在第一層皮底下形成。

One more molt exposes the hard exterior of the pupa.

再一次蛻皮後， 蛹的堅硬外殼就會暴露出來。

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

除了成蟲原基之外， 只有少數組織得以倖免，

including parts of the respiratory system,

包括呼吸系統的某些部分、

the heart,

心臟、

some abdominal muscles,

一些腹部肌肉，

and the mushroom bodies of the brain.

和大腦的蘑菇體。

The caterpillar juice then fuels the development of the imaginal discs

幼蟲的體液會供養成蟲原基發育，

into eyes,

變成眼睛、

antennae,

觸角、

legs,

腳、

wings,

genitalia,

翅膀、

生殖器，

and other body parts.

和其他身體部位。

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

一旦新的身體打造好了， 牠會進行最後一次蛻皮，

shedding the pupal cuticle.

蛻去蛹角質層。

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

從此，牠就是隻新生的蝴蝶， 可以自由飛翔了。

Even after such a dramatic transformation,

即使在這麼巨大的轉變之後，

the butterfly does retain some memories from its caterpillar days.

蝴蝶仍然保有一些 幼蟲時期的記憶。

It’s likely the mushroom bodies of the brain

有可能是因為大腦的蘑菇體

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

把幼蟲時的一些重要知識， 一路帶到了蝴蝶成蟲時。

How did such an involved developmental process come to be?

這個複雜的發展過程 是怎麼形成的呢？

We don’t know for sure.

我們並不確定。

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

主要的理論是，毛毛蟲實際上是

在蛋裡發生的 其他昆蟲生命階段加長版。

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

According to this hypothesis, over millions of years,

根據這個假設，數百萬年來，

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

幼蟲演化出了在蛋外面 進食和生存的能力。

Regardless of how complete metamorphosis originated,

無論完全變態的源頭是什麼，

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

它已經成為了非常多種昆蟲的 生命週期的一部分。

Still, plenty of species get along perfectly well

然而有許多的物種 進行簡單的發育過程就夠用了。

with a simpler developmental process.

What survival advantages might complete metamorphosis provide

完全變態能夠提供 什麼樣的生存優勢，

to make up for the added hassle?

來彌補它帶來的麻煩呢？

For one, it keeps larvae and adults

其一是，它讓幼蟲和成蟲能避免

from competing for the same habitats and food sources.

為相同的棲息地和食物來源競爭。

And while the pupa may seem vulnerable,

雖然蛹可能看起來很脆弱，

this immobile stage can actually be a good way

這個靜止不動的階段

實際上是用來度過一年中 食物短缺時期的好方法。

to pass parts of the year when food is scarce.

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

對我們來說，蝴蝶的 完全變態聽起來非常棒，

as a phoenix rising from its ashes.

就像鳳凰浴火重生一樣。

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

其實這些轉化，無時無刻 不在我們身邊發生。

From the Hercules beetle

從長戟大兜蟲

to the honey bee

到蜜蜂，

to the garden ant,

到花園中的螞蟻，

countless squishy larvae dissolve and emerge

無數的柔軟幼蟲會自溶， 然後再出現，

as armored, aerodynamic, and nimble adults.

成為有保護的、會飛的敏捷成蟲。