Weaving webs of deceit

Green Hornet writes: The other morning I was watching a spider painstakingly weaving its web and thinking what a wondrous sight it was. Legend has it that Robert the Bruce, sitting exiled in his cave, spent much of his time observing a patient arachnid busy about its work. For those who don’t know the story, King Robert the Bruce was born in Scotland’s Lochmaben Castle in 1274. He was Knight and Overlord of the district of Annandale, and in 1306 he was crowned King of Scotland – and immediately started to do what many like him did before and after, which was to try to kick the English and their army out of his country.

After being defeated at the battle of Falkland, Bruce escaped and hid out in a cave for three months. He was at the lowest point of his life and seriously thought about leaving the country and going to live in France – never coming back. According to legend, while he was thinking about what to do, he watched a spider building a web in the cave’s entrance. The spider fell down time after time, but she finally succeeded with her web. Inspired by the spider’s tenacity, Bruce decided to retry his fight and told his men: “If at first you don’t succeed, try, try, and try again.” (Which is doubtless what your mother told you when you flunked at sport or blew an exam.)

He fought on for another eight years, and eventually succeeded in kicking the English out of Scotland.

There’s a spider in Cayman called an Argiope which makes amazing webs. These webs look as if the small black-and-white beastie which wove them had been on a week-long bender – they’re in the shape of a corkscrew. You find them a lot around mangroves and wetland areas. In the US Argiope spiders are commonly called “garden spiders”. These orb weavers can be almost three inches long from leg tip to leg tip and are common in backyard gardens. Although they are large and intimidating, their bite is dangerous only to people who experience severe allergic reactions to insect and spider bites. The University of Michigan reports that Argiope spiders are also called “writing spiders” because of the bold zigzag pattern that they build into their web. I still think it looks like they were hung over!

In fact, spiders come in many shapes and sizes. There’s one kind I really like in Cayman: it’s the crab spider, the wee flat jobbie which zooms around the house and hides under the baseboards. I’ve never seen one weave a web, and occasionally I have to rescue them from the shower stall.

A spider’s web is one of the most impressive architectural feats in nature, capturing morning dew and insect meals with equal grace, but the webbing rarely stands the test of time – especially over millions of years – so researchers have few samples of ancient web to study.

However, New Scientist reports that scientists have found 136-million-year-old amber encasing pieces of web and trapped insects, which helps fill in the gaps in understanding of the origin of orb webs. The finding also indicates that predatory spiders likely played a role in the evolution of flying insects.

Ancient amber

“The hunk of amber, which was collected in Spain, contains 26 web strands with a mite, a wasp leg, and a beetle stuck to some of the thread by visible droplets of web ‘glue’. Although these insects are extinct, their size and diversity match the type of prey caught in modern webs,” the story says.

“‘The advanced structure of this fossilized web, along with the type of prey that the web caught, indicates that spiders have been fishing insects from the air for a very long time,” said study co-author David Grimaldi of the American Museum of Natural History in New York.

The amber is the oldest known example of a web with trapped insects, and although only a few pieces of the web remain, the arrangement of the preserved bits strongly suggests an orb web design. The orientation of the web indicates that it was strung between objects and hung in the air, and the theory goes that the emergence of hanging spider webs might have influenced the evolution of flying insects.

“For example, members of the family Lepidoptera, which includes moths and butterflies, are covered in scales that allow them to tumble out of sticky webs. And it happens that Lepidoptera evolved around the same time that spiders produced these webs,” Grimaldi told New Scientist.”

The types of insects caught in the fossilized web are important pollinators today, and may have been darting from plant to flowering plant when they were captured by the web. Agile, powerful fliers with good vision, such as bees, would also stand a better chance of avoiding webs, much as they do today. Small, weak flies and less nimble fliers would have been, and still are, more commonly ensnared, the article speculates.

How webs work

“The finding sets the minimum age for the common ancestor of the two groups of spiders that weave orb webs, Araneoidea and Deinopoidea,” the article continues. “Because the two groups use different tricks to snag prey – Deinopoids create a Velcro-like surface to catch insects while Araneoids cover their webbing with a sticky ‘glue’ substance – scientists had long believed the orb web design was an example of convergent evolution, a process in which two organisms develop remarkably similar traits.”

Together with the age of the amber fossil, genetic analysis of the two spider families detailed in another paper in the same issue of Science indicates a common origin for orb web design, the story explains. The protein building blocks that make up spider silk are of interest to other scientists and industry because of their remarkable strength, stretchiness, and toughness. Potential applications include better bandages, bulletproof fibers, aerospace tethers, and nets.

Let’s look at tarantulas (though I am sure many of you would rather not). New Scientist reports that spinning webs is instinctive to these hairy beasts, which use the silk for everything from protecting their eggs to lining and concealing their nests.

Now scientists have discovered another silken tool used by a tarantula from Costa Rica. The zebra tarantula produces silk secretions from tiny nozzle-like structures at the tips of its feet. The substance helps the spider stick to vertical surfaces, ensuring a slip-free trek up a steep wall. “I was completely surprised to find that some spiders have tarsal silk,” said research team member Cheryl Hayashi of the University of California, Riverside. “This research is a great example of how much there is still to discover in the world around us.”

Silk specialists

The finding puts a new spin on ideas about the evolution of spiders, forcing scientists to reconsider which came first – the silk-producing structures on a tarantula’s abdomen or the foot spinners. “Spiders are famous for their ability to spin silk from their abdominal spinnerets. But it was previously unknown that any spider could make silk from their feet,” Hayashi told LiveScience.

“This is what scientists have known: Inside a tarantula’s body a silk-spinning factory is hard at work. Special glands whip up batches of silk proteins made from chains of amino acids. The proteins are mixed into a watery solution before being funneled through looping ducts that lead to openings called spinnerets on the outside of a tarantula’s abdomen. The spinnerets act like valves to control the thickness of silk strands. Each tarantula produces five or six types of silk for various uses,” the article reports.

Now there’s one more silk type. “The researchers, led by Stanislav Gorb of the Max-Planck-Institut for Metals Research in Stuttgart, Germany, coaxed zebra tarantulas (Antrodiaetus seemanni) to walk up vertical glass surfaces,” says the story.

“When a spider began to slip, it would send out strands of silk from nozzles at the ends of its eight legs. The tethers put the brakes on the spider’s descent, leaving behind what looked like a series of ‘footprints’ consisting of dozens of thin, silk fibers with diameters 10 times smaller than human hair.”

Tarantulas like this one also have thousands of microscopic hairs on each foot that generate molecular forces between the surface and the spider’s feet – in addition,  foot claws can latch onto rough surfaces for added traction. But during the lab walk, the zebra tarantulas neglected these sticking tactics in favor of the silk strands from their feet.

The Bard noticed, of course

The remarkable web-weaving ability of spiders was noticed, of course, by Shakespeare. In Twelfth Night he writes for Viola: “Oh what a tangled web we weave / When first we practice to deceive.”

It’s like the web of commercial greed that has been woven in Cayman over the past 50 years. We seem to be unable to extricate ourselves from it. Tangled like hapless flies in the sticky residue of the spider’s orbs, we dance to a pretty tune while those like us continue to fly on the same course until they, too, end up in the sticky mess.

Our terrestrial environmental record in Cayman continues to be appalling – we are tangled in a web of overdevelopment and gridlock. We just can’t seem to figure a way out of it. Despite an initial burst of optimism in the early days that the PPM was going to do things differently, we see them heading into the same traps which snared their predecessors.

Two recent events, as the frenzied lead up to the looming election gains frantic speed, highlighted this inability to think outside the box. The first was the announcement that we will continue our road-building frenzy towards the Eastern Districts, accompanied by joyous shouting that the travel time to West Bay is so much shorter now since the Esterley Tibbetts Highway opened, counterpointed by moaning and groaning from those who stagger into town from Bodden Town and Savannah.

The second was the revelation that the National Conservation Council had finally been appointed just in time with a pro-development coven of new members to further emasculate efforts of the Department of Environment and would be approving a few more mega-developments like Dart’s Indigo Hotel plus more destruction of South Sound (what’s left of it). Not to mention the coming home to roost of the incredibly flexible ordinary high water mark which will enable the seas along Seven Mile Beach to soon be entering the hotel and condo lobbies.

And so, orchestrated and conducted by the Lodge, our politicians and their development cronies continue to weave their webs of deceit around the ecological health of this island.

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