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| Research sheds light on mystery of how spiders 'take flight' | Research sheds light on mystery of how spiders 'take flight' |
| (21 days later) | |
| In October 1832 a young naturalist named Charles Darwin watched with delight as hundreds of tiny spiders dangling from short silk threads floated on to HMS Beagle as the ship made for Buenos Aires. | In October 1832 a young naturalist named Charles Darwin watched with delight as hundreds of tiny spiders dangling from short silk threads floated on to HMS Beagle as the ship made for Buenos Aires. |
| Darwin reasoned that the spiders must have flown at least 60 miles before reaching the vessel. But even as he marvelled at their aerial antics, a debate was under way as to how spiders became airborne in the first place. | Darwin reasoned that the spiders must have flown at least 60 miles before reaching the vessel. But even as he marvelled at their aerial antics, a debate was under way as to how spiders became airborne in the first place. |
| Some scientists said the spiders’ silk thread caught the wind and bore them aloft. But others believed the strands became electrostatically charged and in doing so, allowed the spiders to ride Earth’s natural electric fields. | Some scientists said the spiders’ silk thread caught the wind and bore them aloft. But others believed the strands became electrostatically charged and in doing so, allowed the spiders to ride Earth’s natural electric fields. |
| In a new study, scientists at Bristol University weigh in on the issue. They report the first tests of whether electrostatic forces are involved in what aficionados call spider “ballooning”. After a series of experiments performed with spiders in a Faraday cage, they conclude that the creatures can indeed fly on electric fields. | In a new study, scientists at Bristol University weigh in on the issue. They report the first tests of whether electrostatic forces are involved in what aficionados call spider “ballooning”. After a series of experiments performed with spiders in a Faraday cage, they conclude that the creatures can indeed fly on electric fields. |
| When a spider wants to take flight it typically climbs to the top of a plant, tiptoes around, points its abdomen in the air and rapidly ejects up to a metre of silk. In some species, they eject a number of silk strands that spread out like a fan. Either way, in the blink of an eye, the spider is whisked into the air. | When a spider wants to take flight it typically climbs to the top of a plant, tiptoes around, points its abdomen in the air and rapidly ejects up to a metre of silk. In some species, they eject a number of silk strands that spread out like a fan. Either way, in the blink of an eye, the spider is whisked into the air. |
| World's widest web? Flood-hit spiders find higher ground | |
| To capture spiders to study, Erica Morley, who works on sensory biophysics at Bristol, went to a nearby field and set traps in the form of sticks with upturned bottles on the ends. Back at the lab, she introduced the spiders, one by one, to a clear polycarbonate box in a room that doubled as a Faraday cage, meaning it was isolated from the atmospheric electric field. | To capture spiders to study, Erica Morley, who works on sensory biophysics at Bristol, went to a nearby field and set traps in the form of sticks with upturned bottles on the ends. Back at the lab, she introduced the spiders, one by one, to a clear polycarbonate box in a room that doubled as a Faraday cage, meaning it was isolated from the atmospheric electric field. |
| Morley set the box up so she could re-create inside it the kinds of electric fields that are commonly found in nature. On a clear day, the atmosphere’s electric potential might be 120 volts per metre, but it can be tens of times stronger that this when storm clouds gather. | Morley set the box up so she could re-create inside it the kinds of electric fields that are commonly found in nature. On a clear day, the atmosphere’s electric potential might be 120 volts per metre, but it can be tens of times stronger that this when storm clouds gather. |
| When the electric field was off, Morley found that spiders made few attempts to fly off an upright cardboard strip she had put in the middle of the box. But as she ramped up the field, the spiders increasingly took flight. Once aloft, their altitude could then be controlled. “When they take off, you can switch off the electric field and watch them drop, then switch it on and see them rise again,” she said. | When the electric field was off, Morley found that spiders made few attempts to fly off an upright cardboard strip she had put in the middle of the box. But as she ramped up the field, the spiders increasingly took flight. Once aloft, their altitude could then be controlled. “When they take off, you can switch off the electric field and watch them drop, then switch it on and see them rise again,” she said. |
| In further experiments, Morley and Daniel Robert, who studies how organisms sense their environment, bounced laser light off the spiders to reveal how tiny hairs on their legs moved in the presence of electric fields and so helped them to detect them. Together, the findings, reported in Current Biology, suggest that while air currents are surely important for ballooning, spiders may exploit electric fields too. | In further experiments, Morley and Daniel Robert, who studies how organisms sense their environment, bounced laser light off the spiders to reveal how tiny hairs on their legs moved in the presence of electric fields and so helped them to detect them. Together, the findings, reported in Current Biology, suggest that while air currents are surely important for ballooning, spiders may exploit electric fields too. |
| Following Darwin’s voyage on HMS Beagle, scientists have recorded spiders flying for hundreds of miles. They can reach staggering altitudes too, according to some accounts. In 1939, PA Glick, an assistant entomologist at the US Department of Agriculture, published a technical bulletin on the distribution of insects, spiders and mites in the air that claimed to find spiders more than two miles up. Beyond flying, some spiders can skate, and even sail, on water. | Following Darwin’s voyage on HMS Beagle, scientists have recorded spiders flying for hundreds of miles. They can reach staggering altitudes too, according to some accounts. In 1939, PA Glick, an assistant entomologist at the US Department of Agriculture, published a technical bulletin on the distribution of insects, spiders and mites in the air that claimed to find spiders more than two miles up. Beyond flying, some spiders can skate, and even sail, on water. |
| While Darwin described the spiders’ aerial excursions to HMS Beagle as “inexplicable”, ballooning undoubtedly helps to disperse the creatures. And the sooner they start the better. “Spider egg sacs can contain hundreds of eggs and spiders are cannibalistic, so it’s probably advisable to disperse soon after hatching,” Morley said. “It might not be as reckless as we assume.” | While Darwin described the spiders’ aerial excursions to HMS Beagle as “inexplicable”, ballooning undoubtedly helps to disperse the creatures. And the sooner they start the better. “Spider egg sacs can contain hundreds of eggs and spiders are cannibalistic, so it’s probably advisable to disperse soon after hatching,” Morley said. “It might not be as reckless as we assume.” |
| • This article was corrected on 5 July 2018 because an earlier version referred to spiders as insects. This has been corrected. | • This article was corrected on 5 July 2018 because an earlier version referred to spiders as insects. This has been corrected. |
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