Evidence for nanocoulomb charges on spider ballooning silk

TL;DR

This study demonstrates that spiders can use electrostatic charges on their silk to achieve flight in a controlled environment, revealing a new mechanism for spider ballooning independent of aerodynamic lift.

Contribution

The paper provides the first experimental evidence that spider ballooning can be driven by electrostatic forces from silk charges, with estimated charges of at least 1.15 nanocoulombs.

Findings

Spiders can be launched by electric fields in a chamber without air motion.

A minimum charge of 1.15 nC on silk is necessary for lift.

Electrostatic forces can enable spider flight independently of aerodynamic lift.

Abstract

We report on three launches of ballooning $Erigone$ spiders observed in a 0.9 m$^3$ 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 non-uniformly distributed, favoring initial longitudinal mobility of electrons along the fresh silk during extrusion. These results demonstrate for the first time that spiders are able to utilize charge on their silk to attain electrostatic flight even in the absence of any aerodynamic lift.