'Electric' webs are spiders' secret to catching prey

No wonder Electro keeps getting webbed up and punched out by Spider-Man with embarrassing regularity.

 

A team of scientists at Oxford University have discovered that, in addition to being remarkably strong, spider webs also have electrically-conducive properties that allow them to effectively ensnare small prey, pollen, and even pollutants.

 

Fatal attraction

 

The study, which was published in Naturwissenschaften, reveals that a special kind of electrostatic glue covering the surface of the spider’s web allows it to seemingly spring to life, snatching floating particles and insects in mid-flight.

 

 

The scientists performed experiments on samples taken from the web of a garden cross spider. With the aid of a microscopic Faraday cage (a “shield”-like enclosure that contains and maintains an electromagnetic field) the researchers tested the conductivity of a centimeter-long thread of spider silk held in place between two metal holders connected to an ohm-meter (a  device that measures electrical resistance).

 

By taking a charged metal sphere and placing it within close proximity of the strand, the scientists observed that the silk distorted, gravitating towards the sphere. The scientists’ findings held true, regardless of whether the sphere was positively or negatively charged.

 

The team discovered that this phenomenon could also be replicated using the spider’s entire web. Since individual silk strands are lightweight and extremely stretchable, even the tiniest electrostatic force generated by small insects or pollen is sufficient enough to cause a spider’s web to seemingly leap into action and catch its unsuspecting targets.

 

“Everything that moves through the air develops static charge, so it's fascinating to see how spider webs make use of this to actively catch prey,” explained study lead Professor Fritz Vollrath, who has spent decades studying spider silk rather extensively.

 

According to the scientists, this is due to the ion mobility within the miniscule water droplets that the web’s adhesive surface attracts. A combination of the spiders’ naturally compound-rich silk and the droplets (which serve as both glue carriers and electrostatic conductors) imbues the web with these amazing electrostatic properties.

 

"Thus, in a very real sense, the capture spiral becomes active rather than remains passive and extends to entangle charged prey," wrote the researchers.

 

Spider(web)-sense, tingling!

 

However, the scientists also theorize that the “attraction,” though certainly not mutual in the romantic sense, may work both ways.

 

As the glue is powerful enough to have a distorting effect on the Earth’s electric field within range, flying insects could possibly detect (and thus avoid) the sticky trap, with the help of ‘e-sensors’ on their antennae.

 

“Pretty much all flying insects should be capable of sensing electrical disturbances,” said Professor Vollrath, who hails from Oxford’s Department of Zoology. “Their antennae act as 'e-sensors' when the tips are connected to the body by insulating materials, meaning the charge at the tip will be different from the rest of the insect. As insects approach charged objects, the tips of their antennae will move by a small amount, which they may be able to feel.”

 

Professor Vollrath cited bees as a specific example. “Bees already use e-sensors to sense flowers and other bees, so it now remains to be seen whether they might also use them to avoid webs and thus becoming dinner.”

 

Fortunately for spiders, the short range of the web’s electrostatic influence – merely a few millimeters – means that most insects wouldn’t even have sufficient time to dodge.

 

With great electrostatic power…

 

Interestingly, these latest findings also point towards the possibility of harnessing spider webs for practical (and nature-saving) purposes.

 

Since the webs are also effective at catching pollen and airborne particles, the scientists believe that spider webs can be used to assess pollution levels in certain environments.

 

“The elegant physics of these webs make them perfect active filters of airborne pollutants including aerosols and pesticides,” remarked Professor Vollrath. “Electrical attraction drags these particles to the webs, so you could harvest and test webs to monitor pollution levels – for example, to check for pesticides that might be harming bee populations.”

 

Additionally, since a good number of spiders consume their own webs, it’s possible that pollutants can be detected through the spiders’ behavior and silk output. “Many spiders recycle their webs by eating them, and would include any particles and chemicals that are electrically drawn to the web,” Professor Vollrath declared.

 

The professor added that the impact of specific pesticides on the web-building behavior of spiders had already been established in previous studies. “We already know that spiders spin different webs when on different drugs, for example creating beautiful webs on LSD and terrible webs on caffeine. As a result, the web shapes alone can tell us if any airborne chemicals affect the animal's behaviour.”

 

“Everything that moves through the air develops static charge, so it's fascinating to see how spider webs make use of this to actively catch prey. It's a great bonus for us that this also causes them to attract pollutants, making them a cheap and natural way of tracking pesticides and air quality around the world.”

 

Perhaps Spidey should consider formulating stronger electromagnetic webbing of his own: it might make catching criminals so much easier. — TJD, GMA News