Electric spider flight
As everyone knows, spiders lack wings, yet many can ‘fly’ great distances. It has long been known that small spiders can colonize new territories by ‘ballooning’. Even Darwin was amazed by this.1 Having climbed to the top of an exposed plant leaf or stem, the little arachnid reels out a length of silken thread into the breeze before letting go. Tiny spiders may be carried aloft up to 4 km (2.5 miles) above the earth on their little ‘balloons’ to very far-flung (but undetermined) destinations. These are sometimes thousands of miles away.
For some years, it has been suspected that electrostatic forces play a part in this story but it had never been tested.2 Now, ingenious experiments by scientists from the University of Bristol (UK) have confirmed that spiders both sense electrical fields and use them to launch into the air.3 By generating an electric field (‘e-field’) that mimicked what the spiders would naturally experience, they saw their spiders ‘tiptoeing’—straightening their legs and raising their abdomens in the air while releasing silk—exactly the behaviour seen in ballooning spiders in the wild.
It has long been known that small spiders can colonize new territories by ‘ballooning’. Every day, thousands of thunderstorms occur worldwide and these cause the upper atmosphere to be positively charged, compared to the negatively charged planet surface. The resulting atmospheric potential gradient (voltage) between the earth and sky is less pronounced on sunny days than stormy days, but this e-field is real nonetheless.
The silk from a ballooning spider gains a negative charge which repels it from the negatively-charged plant surface and helps launch the tiny spider into the air. The scientists showed that special sensors on a spider’s feet (trichobothria) respond to the electrostatic forces of the e-field so it knows just when conditions are right for take-off.4 Spiders even seem able to control their altitude once aloft.3
So, there’s much more to the seemingly simple spider flight than meets the eye. Ballooning requires electrostatic sense organs, silk spinnerets, correct silk properties and tiptoeing behaviour. All must be in place, pointing to the Marvellous Maker who designed these arachnid aviators.
References and notes
- Darwin, C., Journal of Researches, 2nd Ed., John Murray, London, 1845, p.160; darwin-online.org.uk . Return to text.
- Nunn, W., Charged-up spiders on the move, Creation 38(1):38–39, 2016; creaion.com/charged-up-spiders. Return to text.
- Morley, E.L. & Robert, D., Electric fields elicit ballooning in spiders, Current Biology 28(14):P2324–2330.E2, 23 July 2018 | doi:10.1016/j.cub.2018.05.057. Return to text.
- Yong, E., Spiders can fly hundreds of miles using electricity, theatlantic.com, 5 July 2018; accessed 29 August 2018. Return to text.