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spider orb webs 2 3 Running title: Spider web response to humidity 4 5 Cecilia Boutry * and Todd Alan Blackledge 6 7 University of Akron and Integrated Biosciences Program, University of Akron, Akron, OH 443258 3908, USA 9 *Author for correspondence ([email protected]) 10 11 Abstract 12 Like many biomaterials, spider silk responds to water through softening and swelling. Major ampullate 13 silk, the main structural element of most prey capture webs, also shrinks dramatically if unrestrained or 14 develops high tension if restrained, a phenomenon called “supercontraction”. While supercontraction 15 has been investigated for over 30 years, its consequences for web performance remain controversial. 16 Here, we measure prey capture performance of dry and wet (supercontracted) orb webs of Argiope and 17 Nephila using small wood blocks as prey. Prey capture performance significantly increased at high 18 humidity for Argiope while the improvement was less dramatic for Nephila. This difference is likely 19 due to Argiope silk supercontracting more than Nephila silk. Web deflection, measured as the extension 20 of the web upon prey impact, also increased at high humidity in Argiope, suggesting that silk softening 21 upon supercontraction explains improved performance of wet webs. These results strongly argue that 22 supercontraction is not detrimental to web performance. 23 24