不会飞的甲壳虫如何海上航行 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 . 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 .
One theory , which dates back to 1923 , is that the beetles drift from place to place , buoyed up by a tiny air cavity each has beneath its outer shell , which allows the insects to float .
Dr Huang ' s research into the weevils began when he noted that this theory had never been tested . He discovered , when he put it to the test , that the beetles do , indeed , float .
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 . Clearly , adult weevils are not good sailors .
That does not , however , mean that weevil young are not . Pachyrhynchus weevils have a predilection for laying their eggs inside the fruit of a mangrove - dwelling plant called the fish - poison tree .
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 . Coconuts are protected from being eaten on their travels by having a hard , thick shell .
Fish - poison - tree fruit are also protected from hungry sea creatures . But in their case , as their name suggests , the protection is chemical . 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 .
So he tested this as well . His experiment revealed that such larvae are tolerant of saline conditions . Specifically , of 18 grubs thrown into seawater inside a piece of fruit , two survived for six days .
Moreover , these larvae went on to develop into healthy , sexually mature adults . Two larvae out of 18 surviving for six days at sea might not sound particularly impressive .
But Dr Huang argues that such numbers would easily support island colonisation . He observes , for example , that the Kuroshio Current , which carries water from the Philippines , past Japan and onwards into the Pacific ,
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