Prey attraction as a possible function of the silk decoration of the uloborid spider Octonoba sybotides |
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Authors: | Watanabe Takeshi |
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Institution: | Department of Zoology, Faculty of Science, Kyoto University, Kyoto,
606-8502, Japan |
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Abstract: | Both laboratory experiments and field observations were usedto examine the
prey-attraction hypothesis for the function ofthe silk decoration on the orb
web of Octonoba sybotides. Thereflectance spectrum of the decorative
silk showed that thedecorations reflect relatively more ultraviolet (UV)
light.Choice experiments were conducted using Drosophila
melanogaster,a common prey species of the spider, to determine whether
webswith silk decoration attract more flies than undecorated webs.The choice
experiment showed that webs with silk decorationattract more flies in light
that includes UV rays. However,flies choose their flight direction randomly
in light withoutUV rays. This suggests that the silk decoration might attract
preyinsects that tend to fly toward UV-reflecting objects. Fieldobservations
comparing the prey capture rate between webs withand without a silk
decoration showed that more prey are caughtin decorated webs. In this study,
no difference between thetwo forms of silk decoration, linear and spiral, was
detectedeither in prey attraction in the choice experiment or in theprey
capture rate in the field observations. |
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Keywords: | choice experiment Octonoba sybotides prey attraction prey capture rate silk decoration ultraviolet light |
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