Electrically charged insects perfect prey for spiders

Spider webs take advantage of an electrical charge built up by flying insects to snare their prey suggests a researcher at University of California, Berkeley.

Inspired by his four year old daughter’s toy, Victor Manuel Ortega-Jimenez, a hummingbird flight expert at Berkeley, came up with a new idea about how spider webs attract insects.

Ortega-Jimenez said: “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 realised 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.”

The positive charge on an insect such as a fly or a bee attracts the web which is normally negatively or naturally charged. This increases the chances that a flying insect will make contact with and stick to the web.

Insects develop several hundred volts of positive charge from the friction of wings against air molecules.

Ortega-Jimenez sought out cross-spider (Araneus diadematus) webs along streams in Berkeley and brought them into the laboratory. Using an electrostatic generator to charge up dead insects, he then dropped them into a neutral, grounded web.

“Using a high-speed camera, you can clearly see the spider web is deforming and touching the insect before it reaches the web.”

The control insects that had not been subjected to an electrostatic generator did not do this.

“You would expect that if the web is charged negatively, the attraction would increase.”

For further work, Ortega-Jimenez plans to detect more tests to determine whether this effect happens in the wild. He also wants to know whether static charges on webs attract more dirt and pollen and if that’s a major reason orb weavers rebuilt them daily.

The findings are published in Scientific Reports.