经济学人: 不会飞的甲壳虫如何海上航行（打印版）

　　Pachyrhynchus weevils are found on most islands in the eastern Pacific Ocean. If these weevils could fly, that would not be surprising. But they cannot. 在东太平洋的大部分岛屿中都发现了球背象鼻虫。如果这些象鼻虫会飞的话，也不稀奇。但是它们不会。

　　Why they are so widespread is therefore a mystery. But it is one that Wen-San Huang of the National Museum of Natural Science in Taiwan thinks he has solved. 为什么它们分布如此广布也是个谜。但是台湾国立自然科学博物的黃文山认为，他已解开了这个谜团。

　　One theory, which dates back to 1923, is that the beetles drift from place to place, 回到1923年，当时有一种理论认为甲壳虫总是漂无定所，

　　buoyed up by a tiny air cavity each has beneath its outer shell, which allows the insects to float. 每只甲壳虫外壳的下方都有一个微型的气腔，昆虫们可以借助这个气腔漂浮。

　　Dr Huang's research into the weevils began when he noted that this theory had never been tested. 当时黄博士注意到这个理论从未被验证过，因此他开始了对象鼻虫的研究。

　　He discovered, when he put it to the test, that the beetles do, indeed, float. 在对该理论进行验证时，他发现甲壳虫确实会漂浮。

　　But, as he reports in Experimental Biology, floating in seawater does not do them much good. All 57 adults he tried it with died within two days. 但是，他在实验生物大会上的报告中表示，在海水中漂浮对它们并没有什么好处。他在实验中使用的57只成年甲虫全部于两天内死亡。

　　Clearly, adult weevils are not good sailors. 很明显，成年象鼻虫并不是一名好水手。

　　That does not, however, mean that weevil young are not. 但那并不意味着小象鼻虫也不是。

　　Pachyrhynchus weevils have a predilection for laying their eggs inside the fruit of a mangrove-dwelling plant called the fish-poison tree. 球背象鼻虫偏好把它们的卵产在一种植物的果实中，这种植物被称为鱼毒树，它们生长于红树林中。

　　This reproduces in a way reminiscent of coconut palms. It drops its fruits into the ocean, which carries them away to germinate on distant beaches. 这种繁殖手段让人联想起了椰树。它将果实落入海洋中，这些果实随着海水漂到遥远的海滩上发芽。

　　Coconuts are protected from being eaten on their travels by having a hard, thick shell. 椰子坚硬的厚壳能够在旅途中保护它们不被吃掉。

　　Fish-poison-tree fruit are also protected from hungry sea creatures. But in their case, as their name suggests, the protection is chemical. 鱼毒树的果实也受到了保护不会被饥饿的海洋生物吃掉。但是正如它们的名字一样，保护它们的是一种化学物质。

　　Given the relationship between weevils and plant, Dr Huang wondered how beetle larvae would fare if they were deep inside a piece of fruit floating in seawater. 鉴于象鼻虫和植物之间的关系，黄博士想知道如果象鼻虫的幼虫深藏在这种果实里边，它们是否可以在海中存活。

　　So he tested this as well. His experiment revealed that such larvae are tolerant of saline conditions. 所以他也对此进行了测验。他的研究表明这种幼虫能够忍耐盐性环境。

　　Specifically, of 18 grubs thrown into seawater inside a piece of fruit, two survived for six days. 被扔进海中的果实里边有18只幼虫，其中有2只存活了6天。

　　Moreover, these larvae went on to develop into healthy, sexually mature adults. 而且，这些幼虫继续发育并长成了健康、性成熟的成年虫。

　　Two larvae out of 18 surviving for six days at sea might not sound particularly impressive. 18只中2只在海上存活6天，这个数字或许听起来没那么引人注目。

　　But Dr Huang argues that such numbers would easily support island colonisation. 但是黄博士表示这些数字将轻易为小岛定殖的说法提供支持。

　　He observes, for example, that the Kuroshio Current, which carries water from the Philippines, past Japan and onwards into the Pacific, 例如，他观察到黑潮（自菲律宾开始，穿过日本并向前进入太平洋）

　　moves so swiftly that a piece of fruit caught in it could easily travel 90km in a day. 移动得很快，因此搭上黑潮的果实可以轻易地在一天内漂流90千米。

　　Since it is only 400km from the northernmost islands of the Philippines to the southernmost islands of Japan, 既然菲律宾最北端的岛屿和日本最南端岛屿之间仅隔400千米，

　　a constant migration of larvae in this direction would be easy to maintain—thus solving the question of how a flightless beetle can island-hop so effectively. 幼虫按照这个方向进行经常性迁移将会是轻而易举的—因此也解决了—一只不会飞的甲壳虫如何在岛屿间如此高效来回迁移—的问题。

经济学人: 不会飞的甲壳虫如何海上航行（在线收听）