[ad_1]
In October 1832, a young naturalist by the name of Charles Darwin delighted to observe hundreds of tiny spiders hanging from short silk threads floating on HMS Beagle as the ship was taking him to Buenos Aires
. at least 60 miles before reaching the ship. But even though he was amazed at their aerial antics, a debate was going on about how the spiders got to be in the air in the first place.
Some scientists have said that spider silk caught the wind and carried it in the air. But others believed that the strands were electrostatically charged and, in doing so, allowed the spiders to roll over the natural electric fields of the Earth.
In a new study, scientists from the University of Bristol have looked into the matter. They report the first tests of whether electrostatic forces are involved in what aficionados call "spoon ballooning". After a series of experiments performed with spiders in a Faraday cage, they conclude that creatures can indeed fly on electric fields.
When a spider wants to take flight, she usually climbs to the top of a plant, tip on its tip. abdomen in the air and eject quickly up to a meter of silk. In some species, they eject a number of strands of silk that unfold like a fan. Anyway, in the blink of an eye, the spider is blown into the air.
To capture spiders to study, Erica Morley, who works on sensory biophysics in Bristol, went to a nearby field and set up traps. sticks with spilled bottles on the ends. Back in the lab, she introduced the spiders, one by one, into a transparent polycarbonate box in a room that served as a Faraday cage, which meant she was isolated from the atmospheric electric field.
Morley put the box in place so that she could recreate inside the types of electric fields that are commonly found in nature. On a clear day, the electrical potential of the atmosphere could be 120 volts per meter, but it can be ten times stronger than when clouds gather.
When the electric field was cut, Morley found that spiders made few attempts to fly. from a vertical cardboard tape that she had placed in the middle of the box. But as she increased the field, spiders took more and more flight. Once at altitude, their altitude could then be controlled. "When they take off, you can turn off the electric field and watch them fall, then turn on and see them get up again," she said.
In other experiments, Morley and Daniel Robert, who are studying how organisms feel their environment, swung laser light onto spiders to reveal how tiny hairs on their legs were moving in the presence of electric fields and helped them to detect them. Together, the findings, reported in Current Biology, suggest that while air currents are certainly important to the balloon, spiders can also exploit electric fields.
After Darwin's trip to HMS Beagle, scientists recorded spiders. They can also reach staggering altitudes, according to some testimonies. In 1939, PA Glick, an badistant entomologist of the United States 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 three kilometers away. Beyond the flight, some spiders can skate, and even sail, on the water.
Although Darwin described aerial excursions of spiders to HMS Beagle as "inexplicable", ballooning definitely helps to disperse the creatures. And the sooner they start the better. "Spider-egg sacs can hold hundreds of eggs and spiders are cannibals, so it's probably advisable to disperse shortly after hatching," Morley said. . "He might not be as imprudent as we suppose."
• This article was corrected on July 5, 2018 because an earlier version referred to spiders as insects. This has been corrected.
Source link
