It's not hard to see how an insect could get trapped in a spider's web; its strands are sticky, ultra-strong, and well-concealed. But according to a new study published in the journal Scientific Reports, spiders may also use a more subtle tool to catch their prey: electricity.

In a paper published this week, Victor Manuel Ortega-Jimenez and Robert Dudley of the University of California Berkeley found that spider webs change their shape in response to the electrostatic charges of insects, and that positively-charged bugs are actually attracted to the webs. It has long been assumed that spiders change the shape of their web to catch different bugs, but until now, researchers were unsure as to how they do it.

A girl's toy leads to a 'Eureka' moment

Ortega-Jimenez hypothesized that electricity may hold a clue, after noticing that a spider web changed shape every time his daughter's electrostatically charged toy wand passed in front of it. Intrigued, he and Dudley began collecting strands of spider webs from the UC Berkeley campus, and placed them in front of honeybees, aphids, fruit flies, and water droplets.

Bees and other insects have been shown to generate electricity as they fly, typically by rapidly flapping their wings. In their experiments, Ortega-Jimenez and Dudley found that positively-charged insects were indeed attracted to a spider's web, and that the web would actually change shape. In some cases, the web would bend inward as a flying bee approached, making the insect more likely to get trapped.

But it remains unclear whether this technique is widely used among different spider species. Ortega-Jimenez and Dudley focused their study on the web of a cross spider, which is not known to eat honeybees. The arachnids mostly eat flies, which have yet to be tested for electrostatic charges.