New study shows electrostatic attraction between insects and spider webs

A spider hangs from its web. A recent study from UC Berkeley shows that electrostatically charged insects are attracted to spiderwebs.
Victor M. Ortega/Courtesy
A spider hangs from its web. A recent study from UC Berkeley shows that electrostatically charged insects are attracted to spiderwebs.

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A recent study by UC Berkeley biologists suggests that electrostatically charged insects attract spider webs when they are close, making it easier to be snared by the web.

The research, published online Thursday at Scientific Reports, sheds light on how electrostatic charges affect spider webs in relation to flying insects, which gain a positive charge by flapping their wings and attract spider webs. This attraction results in a larger area for a web to cover and catch potential prey.

Robert Dudley, a campus professor of integrative biology who has done research in insect flight and is one of the lead researchers of the study, explains that any flying object, from small insects to helicopters, gains a positive charge by flying through the air due to friction with the air.

In the laboratory experiment, dead insects were positively charged and dropped on a neutrally charged web that was laid horizontally. With the use of high-speed cameras, researchers observed the spider web bending toward the falling insect before the insect actually touched the web.

When insects carrying no charge were dropped, the web did not bend toward the insect.

“The web would stretch towards the insect, which is very clever,” Dudley said. “It enhances the likelihood of catching an insect.”

Victor Manuel Ortega-Jimenez, a UC Berkeley postdoctoral fellow who first made the observation, said that the next step is to put the experiment to practice in the field to see how the web interacts with live insects.

Ortega-Jimenez, who is finishing a postdoctoral fellowship at University of North Carolina at Chapel Hill, said it will be interesting to see how this relationship will play out, because spider webs tend to be negatively charged in the wild, making the attraction between web and insect stronger.

“If webs are charged, insects have to spend more effort flapping their wings when they are flying,” Ortega-Jimenez said. “How long will it take to get started on the research? I don’t know. It depends on the insects.”

Ortega-Jimenez said that he first observed the web’s attraction to a positive charge when he was trying to teach his daughter about electrostatic charges, using a toy that works as an electrostatic generator that allows one to attract and pick up small objects, such as paper.

“We were outside of our apartment, and we put the wand close to a giant spider web, and there was a strong attraction between the web and the wand,” Ortega-Jimenez said. “It kept on getting closer until the web touched the wand.”

Although the study is new, Dudley and Ortega-Jimenez are surprised by the attention the research has received.

“People don’t like spiders,” Dudley said. “I think they are impressed by the evil practices of spiders in capturing insects.”

Contact Jose Hernandez at [email protected].

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