fir0002 | via Wikimedia Commons // CC BY-NC 3.0
fir0002 | via Wikimedia Commons // CC BY-NC 3.0

The Strength of Spider Web Glue Is Affected by UV Light

fir0002 | via Wikimedia Commons // CC BY-NC 3.0
fir0002 | via Wikimedia Commons // CC BY-NC 3.0

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.

Michael Hutchinson
Spiders Can Fly Through the Air Using the Earth's Electric Field
A spider exhibiting ballooning behavior.
A spider exhibiting ballooning behavior.
Michael Hutchinson

Every so often, otherwise Earth-bound spiders take to the air. Ballooning spiders can travel hundreds of miles through the air (and, horrifyingly, rain down on unsuspecting towns). The common explanation for this phenomenon is that the spiders surf the wind on strands of silk, but there may be other forces at work, according to a new study spotted by The Atlantic.

In the research, published in Current Biology, University of Bristol scientists argue that Earth's atmospheric electricity allows spiders to become airborne even on windless days. To test their hypothesis, the researchers exposed spiders in the lab to electric fields similar to those naturally found in the atmosphere.

When the electric field was turned on, the spiders began to exhibit behavior associated with ballooning—they "tiptoed" on the ends of their legs, raised their abdomens, and released silk. Spiders only exhibit this behavior when ballooning. And when they did become airborne, the spiders’ altitude could be controlled by turning the electric field on and off. When the electric field was on, they rose through the air, but when it was off, they drifted downward.

This provides a potential explanation for why spiders take to the skies on certain days but not others, and how they can fly in calm, windless weather— something scientists have puzzled over since the early 19th century. (Even Darwin was flummoxed, calling it "inexplicable," The Atlantic notes.) However, the researchers note that these electric fields might not be totally necessary for ballooning—wind alone might work perfectly fine on some days, too. But understanding more about when and how spiders become airborne could help us predict when there will be large masses of arachnids flying through the skies (and hide).

[h/t The Atlantic]

How Spiders Surf the Wind For Miles on Strands of Silk

Spiders may very well be hairy and scary, but at least they can’t fly … right? Well, that depends on your definition of flight. As The New York Times reports, new aeronautical research is shedding light on the little-understood phenomenon of “ballooning,” which lets spiders span great distances—even oceans—by riding the wind like paragliders.

Moonsung Cho, an aeronautical engineer, started researching “spider flight” after witnessing a spider being carried by the wind in Denmark. Scientists have long known that spiders sometimes use flight to evade threats or seek food and mates in other locations, but prior to this study, the physics of how it actually works remained fuzzy.

Cho and his colleagues brought crab spiders back to the laboratory and used a wind tunnel to observe their response in a controlled setting. They discovered that a spider will use its leg as an anemometer, lifting one limb to test the strength of the wind. (Their idea of perfect flying weather is a light breeze of about 7 mph.)

Then, the spider lifts up its abdomen, shoots strands of silk skyward, and lets itself be carried off into the sunset. These strands of silk are far thinner than a strand of human hair and can measure up to 6 feet long. As Live Science puts it, a strand of silk contorts when it’s caught in the wind, thus “catching air like an open parachute.” This lets spiders surf the air current, at least for a few miles.

Instances of “spider flight” have been witnessed all over the world. Residents of one Australian town reported seeing a “tunnel of webs” in the sky back in 2015. Spiders sometimes migrate en masse, and although they use the wind to move about, they can’t control where they end up. Some have even landed on islands in the middle of the ocean.

Check out this video from The New York Times to learn more ballooning.

[h/t The New York Times]


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