Biologists from the University of California, Berkeley have discovered that spider webs are more effective at capturing electrically charged insects. The Berkeley scientists say flapping insects can easily develop several hundred volts of positive charge from the friction of wings against air molecules or by contacting a charged surface. This increases the chances they will contact and stick to a spider web, which is negatively or neutrally charged. 

UC Berkeley post-doctoral fellow Victor Manuel Ortega-Jimenez said in a release, "Electrostatic charges are everywhere, and we propose that this may have driven the evolution of specialized webs. I was playing with my daughter's magic wand, a toy that produces an electrostatic charge, and I noticed that the positive charge attracted spider webs. I then realized that if an insect is positively charged too it could perhaps attract an oppositely charged spider web to affect the capture success of the spider web." 

To test his spider web hypothesis, Ortega-Jimenez sought out cross-spider (Araneus diadematus) webs (pictured above) along streams in Berkeley and brought them into the lab. He then used an electrostatic generator to charge up dead insects and drop them into a neutral, grounded web. Ortega-Jimenez says, "Using a high speed camera, you can clearly see the spider web is deforming and touching the insect before it reaches the web. Insects without a charge did not do this. You would expect that if the web is charged negatively, the attraction would increase." 

Fascinating. Makes sense, now that I know.

Great scientific discoveries often happen thusly: "I was playing with my daughter's magic wand, a toy that produces an electrostatic charge ..."