Bombardier Beetle 气步甲

张一恺/文　张建军/译

I will never forget the thrill of discovering that place. A huge clearing unfolded before my eyes， so vast that it revealed the undulating forms of the mountain beneath; a row of trees stretched into the distance forming a neat fence around its perimeter， which suggested that this was the work of professional loggers rather than locals. There was a steady drizzle out here， which was completely unnoticeable earlier in the forest; moon shimmered with a blue radiance， casting down the shadows of dark clouds as they passed over the crescent.

我永远也不会忘记发现这个地方时的兴奋。一块巨大的空地展现在我眼前，巨大到可以由此看到下面起伏的山脉形状；一排树木伸展至遠方，形成了周边整齐的藩篱，表明这是专业伐木工而不是当地人的杰作。天上细雨绵绵，刚才在森林里时我却浑然不觉。月亮闪耀着蓝色的光芒，乌云越过月牙时投下暗影。

I scanned my searchlight across the ground， and instantly picked up the metallic reflections from several ground beetles. As Max had predicted， the muggy atmosphere triggered the activity of thousands of slugs and snails， which in turn lured out the nocturnal predators that preyed upon them. The sight of this swarm was a real confidence boost—Carabus was a predatory ground beetle， albeit of a giant kind， and there should be no reason why it wouldn’t be here to capitalise on the banquet as well. In the space of an hour I collected at least ten different species of ground beetles. Most were about half an inch long and had shiny black shells， which occasionally glowed with a metallic lustre of greens and purples. One kind， however， was garishly dressed in a combination of black and yellow so that it stood out from all the rest. I had never seen such a beautifully coloured ground beetle before， and in the heat of the moment I neglected nature’s most obvious warning sign as I reached my hand towards it—after all， it’s not a wasp， so it can’t sting. Right？

我用手电光搜索着地面，立刻发现了几只步甲身上反射出的金属光泽。正如马克斯预测的，闷热潮湿的环境引发了成千上万只鼻涕虫和蜗牛的活动，这继而又诱出了那些以它们为食的夜行猎食者。看到这一大群虫子，我信心大增：大步甲正是一种掠食步甲，尽管是很大的那种，它没有理由不来此享用盛宴。一个小时之中，我就捉到了至少10种不同的步甲。它们绝大多数约半英寸长，有着亮黑色的甲壳，有时候也会发出各种绿色和紫色的金属光泽。然而，有一种步甲可谓“鹤立鸡群”。它有着炫目的黄和黑的混合色，我以前从来没有看到过色彩如此美丽的步甲。一时兴起，我忽略了自然界最显见的警告标识，朝它伸过手去。毕竟，它不是一只大黄蜂，所以它不会蜇人，对吧？

‘Ouch！’ I gave a yelp of surprise as my fingers burned with a scorching sensation. Leaving behind a high-pitched ‘pop’ and a plume of smoke from its rear end， the beetle had disappeared into the depths of a tussock nearby. A brown stain was left on my fingertips along with an awful lingering smell， but there was no stinger or mark to suggest that I had been stung. Alarm soon turned into elation， as I realised that I had just chanced upon my first bombardier beetle， along with one of nature’s most remarkable events.

“哎哟！”我惊叫起来，手指被灼伤了，带着火辣辣的感觉。随着它尾部发出尖利的“噗”一声，还喷出一团烟雾，这只步甲消失在附近的草丛深处。我的指尖上留下了一个棕色的印子，还伴着久久不散的臭味，但没有螫针或蜇痕显示我被叮咬。当意识到我刚才是第一次巧遇气步甲，还亲历了自然界最令人瞩目的事件之一時，这一惊吓迅速转化为狂喜。

What had happened was a series of extremely complex chemical reactions： the beetle first secreted a fuel and an oxidant into a reservoir chamber， which formed an inert mixture for ease of storage. When I picked it up， a small amount of this mixture was released into a sturdy reaction chamber， which was capable of tolerating high temperatures. The walls of this chamber were lined with enzymes， which triggered a violent reaction within the mixture to form a boiling solution close to 100 degrees Celsius. The massive pressure generated from the heat forced shut the valves leading into the reaction chamber， thus protecting the beetle’s internal organs from the ‘backfire’， and exited through the rear as a controlled explosion. The tip of the abdomen could be rotated freely and the explosion aimed at any angle， since the shortened wing cases had left the tip exposed. As if one explosion wasn’t impressive enough， this cycle was repeated at an astonishing rate of 500 pulses per second—yes， that squeaky ‘pop’ was in fact the sound of over seventy individual explosions！ Even with modern technology， the firing speed of our weapons truly pales in comparison to this biological machine gun.

刚才发生的是一系列极其复杂的化学反应：这只甲虫首先分泌出燃料和氧化剂进入它的“储存舱”，形成一种惰性混合物以便储存。当我抓起气步甲时，少量的混合物会被释放进坚固的反应囊里，反应囊能耐受高温。囊壁上成排的生物酶在混合物里会催化强烈的化学反应，形成接近摄氏100度的沸腾溶液。由热量产生的巨大压力迫使通向反应囊的阀门关闭，以此保护气步甲的内脏免于“逆火”烧灼，而溶液则从尾部喷出，形成可操控的爆炸。由于缩短了的鞘翅能让腹部尖端暴露，气步甲的腹尖可以任意旋转，使爆炸瞄向任何角度。好像一次爆炸不足以让人印象深刻似的，这个循环能以令人瞠目结舌的每秒钟500次的脉冲重复进行——是的，那噗噗响的“爆破声”实际上是超过70次单独爆炸的声音！即便以现代技术衡量，人类武器开火的速度与这生物机枪相比，也实在是黯然失色。

（转载自《丛林瑰宝——一个自然学家的探险笔记》，电子工业出版社，2020）

* 昆虫学家，画家。曾于剑桥大学获自然科学学士学位，于英国帝国理工大学获分子分类学硕士学位，其间曾赴德国马克斯·普朗克研究所参与生态学项目研究。本文节选自《丛林瑰宝——一个自然学家的探险笔记》，该书表达了作者自幼以来对昆虫和自然的挚爱。

** 曾于中国人民大学法学院获法学学士、法学硕士学位，于英国伦敦大学卡斯商学院获理学硕士学位。曾在美国、新西兰、英国及中国香港等地工作多年，现就职于国内某金融机构。