Evidence for Nanocoulomb Charges on Spider Ballooning Silk
PHYSICAL REVIEW E 102, 012403 (2020) Evidence for nanocoulomb charges on spider ballooning silk E. L. Morley1,* and P. W. Gorham 2,† 1School of Biological Sciences, University of Bristol, 24 Tyndall Avenue, Bristol BS8 1TQ, United Kingdom 2Department of Physics & Astronomy, University of Hawaii at Manoa, 2505 Correa Rd., Honolulu, Hawaii 96822, USA (Received 10 December 2019; revised 5 March 2020; accepted 6 March 2020; published 9 July 2020) We report on three launches of ballooning Erigone spiders observed in a 0.9m3 laboratory chamber, controlled under conditions where no significant air motion was possible. These launches were elicited by vertical, downward-oriented electric fields within the chamber, and the motions indicate clearly that negative electric charge on the ballooning silk, subject to the Coulomb force, produced the lift observed in each launch. We estimate the total charge required under plausible assumptions, and find that at least 1.15 nC is necessary in each case. The charge is likely to be nonuniformly distributed, favoring initial longitudinal mobility of electrons along the fresh silk during extrusion. These results demonstrate that spiders are able to utilize charge on their silk to attain electrostatic flight even in the absence of any aerodynamic lift. DOI: 10.1103/PhysRevE.102.012403 I. INTRODUCTION nificant upward components to the local wind velocity distri- bution; whether actual wind momentum spectra provide the The phenomenon of aerial dispersal of spiders using required distributions is still unproven, particularly for takeoff strands of silk often called gossamer was identified and stud- conditions. Even so, recent detailed observations of spider ied first with some precision by Martin Lister in the late 17th ballooning analyzed exclusively in terms of aerodynamic century [1], followed by Blackwall in 1827 [2], Darwin [3]on forces [12] provide plausible evidence that larger spiders can the Beagle voyage, and a variety of investigators since [4–7].
[Show full text]