The Strength of Spider Web Glue Is Affected by UV Light

As you trick or treat today among the ubiquitous giant spiders posed in elaborate fake webs, take a moment to ponder the extraordinary talents of our real arachnid friends. Consider this, for example: Real spiders spin webs covered in an extremely strong natural glue that all but seals the fate of unfortunate insects that bumble into the trap.

Now, scientists are yielding new data about the varying degrees to which different species’ web glue can resist damage by ultraviolet radiation—information that may eventually lead to the development of new, more environmentally friendly adhesive products.

For years, researchers in biologist Brent Opell’s lab at Virginia Tech have been stalking spiders and collecting their webs in order to learn more about how the glue works. They know that spiders secrete tiny droplets containing a special protein as they spin their silken threads. The droplets become sticky once exposed to air, creating the glue-like substance.

That glue’s stickiness can be affected by a variety of conditions, including humidity and temperature. And in a new study recently published in the Journal of Experimental Biology, Virginia Tech scientists report that ultraviolet radiation also affects spider glue—some much more than others.

To test the effects of ultraviolet B (UVB) radiation, the scientists collected fresh webs made by five different species of so-called orb weaver spiders, which make classic wheel-shaped webs. They then harvested the sticky droplets from the web, and exposed them to varying intensities of UVB rays.

Some webs belonged to spider species that prefer to catch their prey in broad daylight. The others came from species that hunt at night or in forests, where webs receive little or no direct sunlight.

“We shocked some of them with UVB radiation under a light like what you might find in a tanning bed, kept some in dark, and then looked at how the drops responded after being subjected to different levels of radiation,” Sarah Stellwagen, the study’s lead author, told mental_floss.

Stellwagen and her team discovered that the glue of spiders that hunt in daylight not only resisted damage from UVB rays much better than those of the nocturnal and shade-loving forest spiders, but was slightly enhanced by it.

What exactly makes some spider web glue better able to withstand UVB rays remains a mystery, at least for now.

“It could be something happening with the protein that UVB rays actually strengthen it [in some species],” Stellwagen said. “Just like the dentist uses UV light to strengthen the bond that they fill your teeth with.”

No one has yet made an adhesive based on the spider’s glue. First, scientists need to better understand the properties and function of the protein from which the glue is created, how it varies from species to species, and how other environmental factors may affect the glue’s stickiness.

But the fact that spider glue is biodegradable, stable for long periods of time, and extremely strong make it a good candidate for biomimicry—the creation of materials inspired by biological substances and processes occurring naturally in plants or animals.

With further study, material scientists could construct new molecules that have similar abilities to resist UVB radiation. That could eliminate the need for UV-stabilizing chemicals that prevent degradation caused by light in manmade adhesives.

“It definitely has uses, and being a green product, it could replace some other products that cause pollution,” Stellwagen said.