Spiders decorate webs with shimmering ornaments to lure prey

December 26th, 2009 - 12:15 pm ICT by ANI  

Washington, December 26 (ANI): A new study has determined that orb-weaving spiders decorate their webs with colorful and shimmering decorations in order to lure their prey to death.

According to a report in Discovery News, spider prey are drawn to their death by colorful ribbons, shimmery fluff, silk tufts and hints of red and green, which are put up by spiders in their webs.

“This is the first study to show that plant-detritus decorations serve as luring signals to attract prey,” said co-author Daiqin Li, associate professor of biological sciences at the National University of Singapore.

The “detritus” in this case consists of bits of leaves, flowers, twigs, bark and any other plant materials that the spider web decorator chooses.

Along with silk-made ornaments, gory-looking prey remains and egg sacks, the plant materials provide the finishing touches to spider webs created by species like Cyclosa ginnaga, which was the focus of this particular study.

Li and his colleagues conducted both lab and field experiments, the latter in the forests of Xishuangbanna, China, to study how spider victims reacted to ornamented versus plain webs.

The researchers discovered that webs with the ornament-like additions lured anywhere from 200 to 233 percent more insect victims than webs without the augmentations.

“The silk items are made by spiders after the completion of the web and just loosely attached to the web spiral, radial or frame silk threads, depending on the species,” explained Li.

As for the plant materials, he said that “the spider usually uses silk to ‘glue’ the debris to the web silk.”

One theory as to why spiders with fancy webs might do better in the food department holds that the spiders can hide behind the bits of plant material and other handiwork to sneak up on prey as well as to escape their own bird predators.

Li and his team, however, found that wasn’t the secret to the spider’s predatory success.

Further studies on the visual systems of birds and typical spider prey, such as bees, determined that both groups could easily spot the spider and its decorations.

“This is a crucial piece in the puzzle, as only then do behavioral data make sense,” said Mariella Herberstein, a senior lecturer in the Department of Biological Sciences at Macquarie University.

“It might be that the ultraviolet component of the color signal is responsible. Insects love UV and just can’t help themselves from flying towards UV,” she explained. (ANI)

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