Study finds spi­ders use elec­tric­ity to fly

Dar­win’s con­jec­ture about static con­firmed

USA TODAY Weekend Extra - - NEWS - Lilly Price

pub­lished Thurs­day ended the long-run­ning de­bate about whether spi­ders can use the silk they weave as a para­chute to fly through the wind or if flight is pow­ered by static elec­tric­ity re­act­ing with silk.

A study by Univer­sity of Bris­tol sen­sory bio­physi­cist Erica Mor­ley con­firmed what Charles Dar­win no­tably ob­served watch­ing hun­dred of spi­ders fly 60 miles across the ocean and land on his ship, the HMS Bea­gle.

Dar­win sur­mised elec­tro­static force was in­volved. Mor­ley and re­searchers backed this up by demon­strat­ing for the first time in a lab how spi­ders use elec­tro­static forces to bal­loon.

When spi­ders launch off from the ground and float through the sky, some­times for thou­sands of miles, it’s due to a “bal­loon­ing process” in which the spi­der raises its ab­domen to the sky, spins 7- to 13-foot-long silk para­chutes and flies away. A pre­vi­ous study con­firmed that spi­ders fly by check­ing the wind and throw­ing out their silk para­chutes at the right time. The study, how­ever, could not ac­count for why the mul­ti­ple silk threads spi­ders use to bal­loon don’t tan­gle in the wind.

Mor­ley’s re­search ac­counts for the lack of tan­gles and ex­plains why spi­ders can fly thou­sands of miles even when it’s not windy. The strands don’t tan­gle be­cause each is re­pelling off an­other in an elec­tro­static force. The study also con­cluded that the weather con­di­tions are not the pri­mary driver of when a spi­der bal­loons but rather if an elec­tric field is present in the at­mos­phere.

“It is rea­son­able to sur­mise that if e-fields are eco­log­i­cally rel­e­vant, spi­ders should be able to de­tect and re­spond to an e-field by chang­ing their be­hav­ior to en­gage in bal­loon­ing,” the study said.

Re­searchers placed Linyphiid spi­ders into a box that lim­ited air move­ment but mir­rored elec­tric fields nat­u­rally present in at­mo­spheric con­di­tions. When the field was turned on, spi­ders showed a “sig­nif­i­cant in­crease in bal­loon­ing.” The change in be­hav­ior demon­strated the spi­ders can de­tect when elec­tric­ity is present.

Once the spi­ders were bal­loon­ing in the air, re­searchers turned the field off. The spi­ders would rapidly fall out of the air to­ward the ground, demon­strat­ing spi­ders need the elec­tric­ity or­der to bal­loon if air flow is lim­ited.

Al­though wind does play an im­por­tant role in the bal­loon­ing process and the sub­se­quent miles spi­ders travel, this study shows that bal­loon­ing be­hav­ior is sparked by elec­tric fields.

GETTY IM­AGES

A new study says spi­ders’ abil­ity to fly through the air is a func­tion of how they use elec­tric­ity.

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