Nature's glue tells spider webs to snatch prey

It is the electrically-conductive glue that pushes spider webs to snatch prey and pollutants, shows research.

The researchers at Oxford University found that the electro-static (stationary or slow-moving electric charges with no acceleration) properties of the glue that coats spider webs causes them to reach out to grab pollutants or flying insects.

The glue spirals can also distort earth's electric field within a few millimetres of the web that may enable insects to spot the webs with their antennae 'e-sensors', said the researchers.

"The elegant physics of these webs make them perfect active filters of airborne pollutants including aerosols and pesticides," said professor Fritz Vollrath of Oxford University's department of zoology, who led the study.

"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," he added.

"Even more fascinating, you would be able to detect some airborne chemicals just by looking at the shape of the webs. The web shapes alone can tell us if any airborne chemicals affect the animal's behaviour," Vollrath said in the study published in the journal titled Naturwissenschaften (meaning the Science of Nature).

Working with Donald Edmonds from Oxford University's department of physics, Vollrath showed that webs like that of the garden cross spider also cause local distortions in earth's electric field since they behave like conducting discs.

Many insects are able to detect small electrical disturbances, including bees that can sense the electric fields of different flowers and other bees.

Electrical disturbances caused by spider webs are extremely short-ranged, so it is not yet clear whether insects would be able to sense them before the web snaps out to grab them.

Either way, it is clear that electrostatic charges play an important role in the insect world, the study said.