Consequences of electrical conductivity in an orb spider's capture web
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- Vollrath, F. & Edmonds, D. Naturwissenschaften (2013) 100: 1163. doi:10.1007/s00114-013-1120-8
The glue-coated and wet capture spiral of the orb web of the garden cross spider Araneus diadematus is suspended between the dry silk radial and web frame threads. Here, we experimentally demonstrate that the capture spiral is electrically conductive because of necks of liquid connecting the droplets even if the thread is stretched. We examine how this conductivity of the capture spiral may lead to entrapment of charged airborne particles such as pollen, spray droplets and even insects. We further describe and model how the conducting spiral will also locally distort the Earth's ambient electric field. Finally, we examine the hypothesis that such distortion could be used by potential prey to detect the presence of a web but conclude that any effect would probably be too small to allow an insect to take evasive action.
KeywordsSilk Electrostatic charges Airborne particles Aerosol Earth electric field
Legend: A section of Araneus diadematus capture thread is observed under a microscope seconds after it has been deposited in the web under RH of 55 %. The thread shows the swelling of the coating followed rapidly by the formation of individual droplets evenly spaced. (MP4 43026 kb)
Legend : Film showing the distortion of an orb web of Araneus diadematus by a metallic sphere of radius 5 mm charged to a voltage of 5 kV. In (a) the Voltage is positive and in (b) it is negative demonstrating that the neutral but electricity-conducting web is equally attracted to the charged sphere in both cases. (MP4 64550 kb)