From making parachutes to building scuba tanks, the arachnids have come up with some fascinating creations
Spider silk is a wonder material that, weight for weight, is stronger than steel, tougher than Kevlar and can be more elastic than rubber. It’s also flexible and antimicrobial. Scientists have used silk to make bulletproof armor, violin strings, medical bandages, optical fiber cables and even extravagant clothing.
“I don’t think people would believe you if you told them, there’s this creature that, if you scaled it up … to the size of the human, it could catch an aeroplane with the material that it makes itself out of itself,” says Fritz Vollrath, an evolutionary biologist at the University of Oxford.
As Community Hubs
Not all spiders are lone hunters. Researchers know of 25 social species out of the 45,000 described. Social spiders often live together in colonies up to 50,000 strong (although a membership of around 1,000 is usually the optimum size). Working together, such an army of arachnids can build impressive homes of silk. The Anelosimus eximius spider colony in South America can spin webs spanning 25 feet in length, constituting one of the largest silken sanctuaries in the natural world.
Only the female members—outnumbering the males upwards of five to one—work together to build, repair and clean their home. The large numbers of the colony and gargantuan web come in handy when the spiders go after larger prey that an individual can’t take on alone. The spiders work as a team to bring down these larger insects, such as grasshoppers or butterflies, by overwhelming the victims with their numbers.
If the Anelosimus webs are disturbed by predatory swarms of ants or wasps, the spider troops can mount a defense in return. The vibrations of the interlopers are easily transmitted to the vast webs, which disables any surprise attack. The victor of the battle, spider or otherwise, will have a bountiful meal from the fallen.
As Drinking Fountains
While spiders usually quench their thirst by sucking on the juices of their prey, they can also hydrate themselves the traditional way by imbibing directly from water droplets or small puddles. To save themselves a trip to a water hole, they occasionally sip on the droplets that condense on their web.
Spider silk can be excellent at drawing moisture from the air. Researchers studied the silk of cribellate spiders and found that the key to its water collecting property is the fiber’s shifting structure itself. In the presence of humidity, the filaments scrounge up into knotty puffs spaced between smooth untangled strands to look like threaded beads on a string. These knotty puffs are moisture magnets. When water condenses onto the silk, the droplets will slide along the smooth regions towards the puffs and coalesce into larger globules there.
The knobby structure of this silk is so efficient at sucking water out of thin air, that it has inspired scientists to develop similar materials in hopes to harvest water from fog.
As Food
The proteins in spider silk are a valuable commodity. Making silk demands energy on the spider’s part, so sometimes it will eat its own silk, allowing its body to recycle the proteins to make new silk. Many spiders routinely tear down their webs and begin again, so they may as well recycle their building materials.
The Argyrodes spider, or dewdrop spider, takes silk eating to a whole new level—by robbing other spiders’ silk. This spider is a kleptoparasite, which means it pilfers the insect bounty of other spiders rather than hunt for its own. It occasionally does more than steal—it may even move in and prey on the host. During lean times when other spiders can’t land a catch, dewdrop spiders will still steal from the poor by eating the host’s webs instead. Their web heist is a temporary foraging strategy to get by when food is scarce for everyone. Researchers have observed in the lab that the veritable thieves can gorge on the same amount of silk as they would insects.
As Wrapping Paper
A nursery web spider is called what it is for good reason: the females are well-known for constructing a conspicuous egg sac out of silk as a nursery. Mothers are fiercely protective—they will carry their egg sacs in their jaws wherever they roam. When the eggs are about to hatch, the mother will spin a nursery “tent” and place the eggs inside. Then, she stands guard outside and fends off predators until her young are old enough to make their own way out into the world.
Females aren’t the only ones with a creative use of silk. Males spin the material into wrapping paper. As a token of sincerity, a male nursery web spider uses his silk to gift wrap a food item and present it to a suitor. The cost is high if he shows up empty handed: The female usually eats him. Nuptial gifts, as the silk-wrapped dowries are called, help prevent sexual cannibalism by females and extend mating time, keeping the legged ladies occupied with unwrapping presents as males have their way with the females. Researchers have demonstrated that a female is over six times more likely to eat a prospective mate if he shows up sans souvenir, whether she’s hungry or not.
As Bondage During Mating
Prospective brides of many spider species are fearsome creatures—they may eat any male who dares approach. A male spider may thwart a female from eating him by binding her with his silk before mating.
Some spiders restrain the female by tying her entire body to the ground; other males throw over their brides a light veil of silk that’s infused with pheromones to turn her on. Researchers have shown that this sparse silk also soothes the female like would a weighted blanket. The Ancylometes bogotensis spider trusses a female up only by the legs, then tips her on her side to mate with her. This foreplay is done out of sheer necessity—females are generally bigger and more aggressive than the males. In the case of Nephila pilipes, the female is ten times larger and 125 times heavier. And females have no trouble freeing themselves from the bindings after mating.
As a Chemical-Soaked Road
Wandering wolf spider females play hard to get. To broadcast that they’re single and ready to mingle, they’ll leave a trail of silk as they roam. This ‘silk road’ contains sex pheromones, coy come-hither chemical signals that will send males on a merry chase. In fact, males of a particular species of wolf spiders, the Schizocosa ocreata, are able to distinguish the virgin adults from the prepubescent females from the chemicals in the silk fibers. They prefer to chase the sexually mature females to boost their reproductive success.
As a Communication Tool
Spiders are extraordinarily sensitive to vibrations. They can sense their prey through the miniscule tremors in the silk. Silk also provides the perfect platform for arachnids to communicate from a distance by plucking the strands or rumbling their abdomens. Spiders may communicate back and forth along a silk thread during courtship, so a male can test the waters before approaching a standoffish female to avoid getting eaten. If the female is receptive, she might just strum back.
Spiders, if it still isn’t clear, can be devious creatures. One cannibalistic spider has learned how to mimic the vibrations of an insect caught in a trap. It drops by other spiders’ webs, strums its song to lure victims into a corner, then ambushes them. The Portia jumping spider is famous for its intelligence, using trial and error to “compose” the right signals until they successfully pique the curiosity of prey. One particularly persistent Portia has been observed to keep up its experimental strumming for three days, before its prey finally decided to investigate.
Portia spiders will make a move on any spider that’s up to twice its size, so when dealing with the larger spiders, the cannibals need to quiver with caution, lest they become the prey instead. Again, this brainy spider experiments with different beats, perhaps plucking a monotonous melody that calms larger spiders. Or, its rhythm may orient the victim-to-be in a particular direction so the Portia may attack its prey from a safer angle. The impressive range of Portia’s tactics is the hallmark of the spider-eat-spider world that arachnids live in.
“[Spiders] have taken every single possible aspect of being a spider and just run with it in completely different directions,” says Echeverri.“Spiders do ‘spider’ in completely different ways.”
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