Like so many winged insects,  the world's roughly 4,000 mayfly species take to the skies for their annual reproductive ritual.

和许多有翼昆虫一样，世界上大约有4000种蜉蝣物种会飞上天空进行一年一度的繁殖仪式。

These flights happen above every kind of freshwater body on Earth, barring Antarctica and a few remote islands.

这些飞行发生在地球上各种淡水体上方，南极洲和一些偏远岛屿除外。

But whether the breeding mayflies are large Hexagenia limbata, tiny Paracloeodes minutus, or the thousands of species in between,

但无论繁殖的蜉蝣是大型Hexagenia limbata蜉蝣、微型类滑爪蜉，还是介于两者之间的数千种物种，

their time on the wing will be brief.

他们飞行的时间将会很短暂。

Very brief.

非常短暂。

For most mayflies, adulthood lasts roughly one day.

对于大多数蜉蝣来说，成年期大约持续一天。

And for some species, it's only a matter of minutes.

对于某些物种来说，这只是几分钟的问题。

This isn't because they're all eaten up by predators— though they are a favorite food of many fish, birds, and larger insects.

这并不是因为它们都被掠食者吃掉了--尽管它们是许多鱼类、鸟类和大型昆虫最喜欢的食物。

Rather, this abridged adulthood is a natural part of their life cycle.

相反，这种短暂的成年是他们生命周期的自然组成部分。

A close look at these insects reveals they've ditched functional mouths and digestive systems.

仔细观察这些昆虫会发现它们已经放弃了功能性的嘴和消化系统。

Without these innards taking up space, mayfly bodies can store more eggs, with some species producing up to 12,000 per individual.

如果这些内脏不占用空间，蜉蝣的身体可以储存更多的卵，某些物种每个最多可产卵12000个。

This adaptation is essential to mayfly survival since relatively few of these unborn flies are likely to reach adulthood,

这种适应对于蜉蝣的生存至关重要，因为这些未出生的蜉蝣中可能成年的数量相对较少，

and even fewer will successfully reproduce themselves.

成功繁殖的人就更少了。

In most of these flights, male mayflies form dancing swarms, which female mayflies move through until a male grasps them for some mid-air mating.

在大多数这些飞行中，雄性蜉蝣会形成跳舞的蜂群，雌性蜉蝣会在其中移动，直到雄性蜉蝣抓住它们进行一些空中交配。

Some all-female populations can reproduce without joining in the dance,

一些全雌性种群无需参加舞蹈即可繁殖，

using a process called parthenogenesis to produce viable offspring without the help of a male.

利用一种称为单性生殖的过程在没有雄性帮助的情况下产生可行的后代。

And recent research suggests some mayfly populations may even switch back and forth between these two forms of reproduction.

最近的研究表明，一些蜉蝣种群甚至可能在这两种繁殖形式之间来回切换。

But regardless of how the eggs are made ready, the female will deposit them on or under the water, and promptly perish.

但无论卵如何准备好，雌性都会将它们产在水面或水下，并迅速消亡。

This might sound like a tragically brief existence.

这听起来可能像是一个悲惨的短暂存在。

And even mayflies' scientific name, Ephemeroptera, refers to their stunningly short lifespan.

甚至连蜉蝣的学名“Ephemeroptera”也指的是它们短得惊人的寿命。

But for centuries, fishermen suspected that mayflies live much longer than this short flight.

但几个世纪以来，渔民们都怀疑蜉蝣的寿命比这种短途飞行要长得多。

And in 1681, scientists finally caught up to their fishing friends with a published account of the full mayfly life cycle.

1681年，科学家们终于用一本关于蜉蝣整个生命周期的公开账号找到了他们的钓鱼朋友。

When the time is right, these eggs will hatch.

当时机成熟时，这些蛋就会孵化。

Depending on the kind of mayfly, this can happen as late as several months after the egg is laid,

根据蜉蝣的种类，这种情况可能会在产卵几个月后发生，

or even before it's completely left the mother's body.

甚至在它完全离开母亲的身体之前。

But whenever their egg opens up, the mayfly inside quickly finds its way into fresh water, and it's in this aquatic,

但每当它们的卵破开时，里面的蜉蝣就会很快进入淡水，它就在这个水生的，

nymph stage that mayflies spend the majority of their lives.

若虫阶段度过一生大部分时间。

Inhabiting rivers, small streams, ponds, lakes, and other places with clean fresh water,

居住着河流、小溪、池塘、湖泊等拥有清洁淡水的地方，

most mayfly species stay in this nymph stage and feed underwater for nearly an entire year.

大多数蜉蝣物种都停留在这个若虫阶段，并在水下觅食近一整年。

In fact, some species live as nymphs for up to two years before they metamorphose into their winged adult state.

事实上，有些物种在蜕变为有翼的成年状态之前，会以若虫的身份生活长达两年。

A year is a long time for such a small creature to stay alive.

对于如此小的生物来说，一年的时间已经很长了。

So to survive and thrive, mayfly species have a wide variety of habits and corresponding body forms.

因此，为了生存和繁衍生息，蜉蝣物种有着多种多样的习惯和相应的体型。

Sprawlers are flat enough to stick to surfaces despite the strength of a current, while clingers accomplish the same feat with suckers and claws.

蔓延型足够平坦，即使水流强度很大，也可以粘在表面上，而附着型则可以用吸盘和爪子完成同样的壮举。

Other species are swimmers, crawlers, or borers.

其他物种是游泳者、爬行者或钻孔虫。

One of the most noticeable groups are the burrowing mayflies; sizable specimens which use their legs, tusks,

最引人注目的群体之一是穴居的蜉蝣;相当大的标本使用它们的腿、长牙，

and a scoop on their heads to dig U-shaped tunnels.

头上的一把铲子，挖U形隧道。

In these muddy dwellings, the nymphs use their abdominal gills to accelerate water through their burrow, filtering it for food along the way.

在这些泥泞的住所中，蚯蚓利用腹鳃加速水通过洞穴，沿途过滤水获取食物。

After they metamorphose, adult swarms can get so large they appear on weather radars like rain.

在蜕变后，成年群会变得如此之大，以至于像雨一样出现在天气雷达上。

Regardless of how they've adapted, each unique species plays an essential role in their ecosystem.

无论它们如何适应，每个独特的物种都在其生态系统中发挥着至关重要的作用。

Plus, nearly all mayflies are a staple of freshwater fish diets, and since they ingest the smallest particulate matter in their environment,

此外，几乎所有的蜉蝣都是淡水鱼饮食的主要成分，由于它们摄入环境中最小的颗粒物，

mayflies are also very sensitive to water pollution.

蝠鲼对水污染也非常敏感。

In fact, scientists can tell a lot about a water body's health based on which mayfly species they find.

事实上，科学家可以根据他们发现的蜉蝣物种来了解水体的健康状况。

If they don't find mayflies at all, it's usually an indication that something is wrong.

如果他们根本找不到蜉蝣，通常表明出了问题。

So the next time you see a swarm of mayflies over a pond, bridge, or park fountain,

因此，下次当你在池塘、桥梁或公园喷泉上看到一群蜉蝣时，

remember that their short aerial dance means a healthy world exists below the surface.

请记住，他们短暂的空中舞蹈意味着表面之下存在着一个健康的世界。