Spi­ders send up silk to take to the skies

World of Animals - - Defying Gravity -

Web-spin­ning species pro­duce ex­tremely fine film-like threads de­signed to catch wind like the sails of a dinghy. Spi­der­lings are most likely to per­form this dar­ing feat as a means to dis­perse them­selves far away from their place of birth and their closely re­lated fam­ily.

Be­fore em­bark­ing on its aerial ad­ven­ture, the spi­der will climb to a high el­e­va­tion and test the air by lift­ing a leg. It will only take off if con­di­tions are per­fect. Up to four me­tres (13.1 feet) of silk are flung into the sky, and the spi­der keeps its legs out­stretched through­out the jour­ney.

It’s no se­cret that the weather can change sud­denly, and bal­loon­ing spi­ders take an enor­mous risk. The arach­nids have no con­trol over their move­ments once they have taken flight, and they are com­pletely at the mercy of the wind. Able to forgo food for 25 days, baby float­ing spi­ders have been dis­cov­ered at el­e­va­tions of five kilo­me­tres (3.1 miles) and even in the mid­dle of the ocean.

Below The silk strandsspi­ders use to fly can be just 100 nanome­tres wide. A hu­man hair is 80,000–100,000 nanome­tres wide

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