Spiders decorate their webs with light waves to trap prey

June 13th, 2008 - 3:05 pm ICT by ANI  

National Geographic

Washington, June 13 (ANI): Australian scientists have discovered that spiders trap their prey by luring it with light waves that they use to decorate their webs with structures like with crosses, zigzags and spirals.

“We really wanted to find out why the spiders were making a substantial investment in decorating their webs,” National Geographic News quoted Dieter Hochuli, one of the authors of the study, as saying.

Some experts are of the opinion that the spider uses such designs to flag the webs presence so that large animals do not walk or fly into them, while others argue that the designs themselves lure prey.

Writing about their study in the Biological Journal of the Linnean Society, the researchers point out that many flower species reflect ultraviolet light that insects use to identify food sources.

They say that they started their study on the assumption that the spiders webs might be mimicking the same properties of flowers to trick insects into coming closer.

Hochulis team coated Saint Andrew’s Cross webs in gardens near the University of Sydney with an ultraviolet filtering plastic, and then monitored what insects were caught daily in both filtered and unfiltered webs.

The researchers observed that flies, bees, wasps, and mosquitoes were all common catches on both filtered and unfiltered webs.

It was also observed that the overall numbers of most species dropped in filtered webs.

Mosquitoes, which do not see ultraviolet light, were unaffected by the filters, say the researchers.

Based on their observations, the researchers came to the conclusion that the webs might be essentially setting a “light trap”, where the reflection of the web strands lure passing insects to their deaths.

“Interestingly, the webs (decorated with crosses) were a little more sophisticated than we first thought,” Hochuli said.

“The spiders seem to be exploiting the sensitivity of some prey to UV light in particular. When we filtered different components of the visual spectrum from webs we dramatically altered prey-capture rates,” he added.

Catherine Craig, an entomologist at Harvard University, who was not involved with the study, said: “This confirms the research that I did earlier in the field and laboratory. UV-reflecting decorations spun by [this] species appear to attract prey.”

She revealed that the research team was planning to further explore the effect of the decoration pattern itself. (ANI)

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