Original image
Daniel Mihailescu/AFP/Getty Images

8 Silkily Engineered Facts About Spider Webs

Original image
Daniel Mihailescu/AFP/Getty Images

If you’re not a fan of spiders, you’re far from alone. But before you swat away another spider web, remember this: Relative to weight, the strength of a spider web rivals steel and Kevlar, the material used to make bullet-proof vests. (That’s important when your dinner flies headlong into your trap and writhes violently as it tries desperately to escape.) This tensile strength has inspired humans to develop a surprising number of products—but it’s just one of the fascinating facts that may give even arachnophobes a new appreciation for these eight-legged architects.


Spiders are like tiny silk production factories. Inside their bodies, thread is stored as a highly concentrated liquid. A common garden spider can produce as many as seven types of silk, each made up of a different sequence of proteins. Each type of thread serves a distinct purpose: one, for example, makes the web stretchy to better absorb the impact of insects smacking into it; another makes the thread less brittle. Still other proteins protect the threads from bacteria and fungi, and keep it moist.


In fact, the silk itself isn't sticky. Picture a classic web, like one made by an orb weaver spider: The basic structure includes radial threads that extend out like wheel spokes from the center. Another set of threads spiral out in concentric circles. The silk used to construct these two parts of the web is actually produced by different glands, which is why one is sticky and the other isn’t.

The silk’s gumminess comes from a super strong polymer adhesive produced by another gland in the spider’s abdomen. The spider secretes droplets of this adhesive along the spiral threads of the web to catch its prey. Most spiders leave the center of the web free of this “glue” so that they can move around with ease. But when the spider needs to travel along the sticky threads of its web, it has a special tool: tiny claws on its legs help it keep from getting stuck.


A frozen web on a mailbox, captured on January 10, 2009 in Fetcham, England. Image Credit: Peter Macdiarmid/Getty Images

The adhesive droplets that spiders apply to their silk become sticky only when the silk leaves the spider’s body. But its strength can be affected by environmental factors, including humidity and temperature. Recently, scientists discovered that ultraviolet radiation also affects the glue. In a series of experiments, researchers found that spiders inhabiting bright, sunny places, such as common garden spiders, produce webs better able to withstand UV radiation than those of nocturnal spiders and forest dwellers, where webs are generally less exposed to direct sunlight.


Webs are used for trapping prey, but spiders produce silk for other reasons, too. Hunting spiders often make silk to use as drag lines to trail behind them as safety nets while they walk and stalk. Other spiders use a specialized silk to create egg sacs, or even to build a little protective shelter for themselves. Perhaps most remarkably, some spiders use their silk to pick up air currents and go sailing up into the sky, sometimes migrating hundreds of miles. When conducted en masse, these so-called mass ballooning events can involve millions of tiny spiders. When they land—or if they have an unsuccessful takeoff due to unfavorable winds—their silken strands can blanket the ground in thick white layers, as they did in Memphis near the end of 2015.


Argentinian artist Tomas Saraceno makes "spiderweb sculptures," seen here as part of the exhibition "A Brief History of the Future" at the Louvre museum in Paris in September 2015. Image Credit: Patrick Kovarik//AFP/Getty Images

Sometimes called the garden center spider for its love of humid greenhouse conditions, the feather-legged lace weaver has a truly far-out way of catching a meal. Researchers at Oxford University discovered that, rather than spinning sticky webs like orb weavers, this spider produces an incredible nano-thin silk inside a special organ called the cribellum. It uses special hairs on its hind legs to comb the silk as it emerges from the body, creating an electrostatic charge in the process. Together, the charged threads form “poofs,” similar to a ball of wool, that trap prey.


Several webs of the Darwin's bark spider spanning A) a river and B) a stream in Madagascar. Image Credit: © 2010 Agnarsson et al. in PLOS One

The female Darwin’s bark spiders build enormous webs—some extending more than 80 feet—across rivers and lakes. By building their super-strong web across the water like a bridge, they can catch large insects like dragonflies that quickly swoop and rise along the water’s surface. The female will spend days building and reinforcing the so-called bridge lines that she casts across rivers to anchor the web on each bank, and repairing damage to the center caused by large insects. Meanwhile, the male of the species, which is considerably smaller than the female, hangs out in plants close to the webs to watch the show from the sidelines. Scientists are racing to learn more about this newly described species as deforestation in Madagascar diminishes their habitat.


In Europe and Asia, the diving bell spider has carved out an extraordinary niche. It spends its entire life underwater—the only spider known to do so. It can survive underwater because of its bell-shaped web, which it anchors to aquatic plants, with additional lines of silk extending up toward the surface. The spider climbs these lines of silk and lifts its rear out of the water to collect air bubbles around the tiny hairs that line its legs and abdomen. Carefully holding the air bubbles between its back legs, it descends back to its bell-shaped web and places the bubbles inside to form one large bubble. Scientists recently discovered that the bell can also take up dissolved oxygen from the water, behaving as a kind of gill. If the spider isn’t very active, this combined oxygen supply can last it an entire day.


Because spider silk is so flexible, light, strong, and water resistant, it has a ton of potential applications. Researchers are busy developing bioinspired, synthetic versions of spider silk like this “liquid wire,” as well as adhesives based on their sticky glue-like protein droplets. Taking inspiration from spider silk, researchers have recently made big strides in designing medical devices, parts, and supplies that need to be strong and stretchy or sticky. These include artificial tendons, ligaments, and implants, as well as sutures, adhesives, and bandages. Spider silk protein is also aiding in the design of textiles and protective products that need to be strong and flexible but also light, like body armor, airbags and even athletic helmets.

But while scientists may draw ideas from spiders, actually using spider silk or protein has one major drawback: harvesting enough to facilitate commercial scale production of these items. So researchers have turned to transgenics—inserting the genes for spider silk inside other organisms. Like E. coli bacteria, which reproduce quickly. And goats. Yes, goats. By implanting spider DNA in goats, scientists can harvest components of spider silk from their milk. The hope is to eventually be able to extract those proteins on a scale large enough to support mass production.

So the next time you recoil in disgust at a spider, remember: You’re dissing a tiny master of engineering.

Original image
25 Benefits of Adopting a Rescue Dog
Original image

According to the ASPCA, 3.3 million dogs enter shelters each year in the United States. Although that number has gone down since 2011 (from 3.9 million) there are still millions of dogs waiting in shelters for a forever home. October is Adopt a Shelter Dog Month; here are 25 benefits of adopting a shelter dog.

Original image
Brooklyn Museum, Charles Edwin Wilbour Fund, 37.406E
New Smithsonian Exhibit Explains Why Felines Were the Cat's Meow in Ancient Egypt
Original image
Brooklyn Museum, Charles Edwin Wilbour Fund, 37.406E

From bi-coastal cat cafes to celebrity pets like Lil Bub, felines are currently enjoying a peak moment in popular culture. That’s part of the reason why curators at the Smithsonian’s Arthur M. Sackler Gallery—which will re-open to visitors on Saturday, October 14, following a 3-month closure—decided to dedicate a new exhibition to ancient Egypt’s relationship with the animals.

Divine Felines: Cats of Ancient Egypt” looks at the cultural and religious importance of cats, which the Egyptians appreciated long before YouTube was a thing and #caturday was a hashtag. It's based on a traveling exhibition that began at the Brooklyn Museum in New York City. On view until January 15, 2018, it's one of several exhibits that will kick off the grand reopening of the Smithsonian’s Freer and Sackler galleries, the conjoined national museums of Asian and Middle Eastern Art.

The Freer has been closed since January 2016 for major renovations, and the Sackler since July 2016 for minor ones. The upgraded institutions will make their public debut on October 14, and be feted by a free two-day festival on the National Mall.

Featuring 80 artworks and relics, ranging from figurines of leonine deities to the tiny coffins of beloved pets, "Divine Felines" even has a cat mummy on loan from the Smithsonian’s National Museum of Natural History. These objects span from the Middle Kingdom (2008 to 1630 BCE) to the Byzantine period (395 to 642 CE).

An ancient Egyptian metal weight shaped like a cat, dating back to 305 to 30 BCE, on view at the Smithsonian’s Arthur M. Sackler Gallery
Weight in Form of a Cat, 305 to 30 BCE, Bronze, silver, lead
Brooklyn Museum, Charles Edwin Wilbour Fund, 36.114

The term “cat” is used loosely, as the Egyptians celebrated domestic mousers and fearsome predators alike.

“The Egyptians were close observers of nature, so they were observing cat behaviors,” Antonietta Catanzariti, the exhibition's in-house curator, tells Mental Floss. “They noticed that cats and lions— in general, felines—have aggressive and protective aspects, so they associated those attributes to deities.”

The ancient Egyptians viewed their gods as humans, animals, or mixed forms. Several of these pantheon members were both associated with and depicted as cats, including Bastet, the goddess of motherhood, fertility, and protection; and Sakhmet, the goddess of war and—when appeased—healing. She typically has a lion head, but in some myths she appears as a pacified cat.

A limestone sculptor's model of a walking lion, on display at the Smithsonian's Arthur M. Sackler Gallery.
Sculptor's Model of a Walking Lion, ca. 664 to 630 BCE, limestone
Brooklyn Museum, Charles Edwin Wilbour Fund, 33.190

While Bastet was a nurturer, Sakhmet—whose name means “The Powerful One”—could use her mighty force to either slay or safeguard humanity. These characterizations are typical of the ancient Egyptian worldview, which perceived the universe in dualistic terms. “There’s always a positive and a negative,” Catanzariti explains.

Contrary to popular belief, however, ancient Egyptians did not view cats themselves as gods. “The goddess Sakhmet does have the features as a lion, or in some cases as a cat, but that doesn’t mean that the Egyptians were worshipping cats or lions,” Catanzariti says. Instead, they were simply noting and admiring her feline traits. This practice, to an extent, also extended to royalty. Kings were associated with lions and other large cats, as they were the powerful protectors of ancient Egypt’s borders.

These myriad associations prompted Egyptians to adorn palaces, temples, protective amulets, ceremonial vessels, and accessories with cat images. Depending on their context, these renderings symbolized everything from protection and power to beauty and sexuality. A king’s throne might have a lion-shaped support, for example, whereas a woman’s cosmetics case might be emblazoned with a cat-headed female goddess of motherhood and fertility.

An ancient Egyptian figurine of a standing lion-headed goddess, on display at the Smithsonian's Arthur M. Sackler Gallery.
Figurine of a Standing Lion-Headed Goddess, 664 to 630 BCE, Faience
Brooklyn Museum, Charles Edwin Wilbour Fund, 37.943E

While cats were linked with heavenly figures and kings, they were also popular domestic pets. Their ability to catch vermin made them an important addition to households, and owners loved and anthropomorphized their pets just like we do today.

Egyptians often named, or nicknamed, their children after animals; Miit (cat) was a popular moniker for girls. It's said that entire households shaved their eyebrows in mourning if a house cat died a natural death. Some also believe that cats received special legal protection. (Not all cats were this lucky, however, as some temples bred kittens specifically to offer their mummified forms to the gods.) If a favorite cat died, the Egyptians would bury them in special decorated coffins, containers, and boxes. King Tutankhamen, for example, had a stone sarcophagus constructed just for his pet feline.

An ancient Egyptian bronze cat head adorned with gold jewelry, on display at the Smithsonian's Arthur M. Sackler Gallery.
Cat's Head, 30 BCE. to third century CE, bronze, gold
Brooklyn Museum, Charles Edwin Wilbour Fund, 36.114

“Divine Felines” breaks down these facts, and more, into five thematic sections, including “Cats and Kings"; “Cats and Gods”; “Cats and Death”; “Cats and Protection”; and “Dogs as Guardians and Hunters.” Yes, there’s also an exhibition section for dog lovers—“a small one,” Catanzariti laughs, that explains why canines were associated with figures like Anubis, the jackal-headed god of mummification and the afterlife.

Did the ancient Egyptians prefer cats to dogs? “I would say that both of them had different roles,” Catanzariti says, as dogs were valued as hunters, scavengers, and guards. “They were appreciated in different ways for their ability to protect or be useful for the Egyptian culture.” In this way, "Divine Felines" is targeted to ailurophiles and canophiliacs alike, even if it's packaged with pointed ears and whiskers.

An ancient Egyptian cat coffin, on display at the Smithsonian's Arthur M. Sackler Gallery.
Coffin for a Cat, 664 to 332 BCE, or later, Wood, gesso, paint, animal remains
Brooklyn Museum, Charles Edwin Wilbour Fund, 37.1944Ea-b


More from mental floss studios