Tag Archives: arachnids

Aqualung

Yesterday’s post was dedicated to spider silk and many of its wondrous uses. Today’s post is about the most wondrous use for spider silk of all. But first, an interlude to talk about comic books.

You know how Spiderman uses his synthetic webbing for all sorts of purposes beyond “slinging”? Sure, there’s the “getting around” webbing, but he can also gift-wrap criminals, or use the “silk” as a projectile glue-bomb that blinds them. He can spin webbing that acts like an airfoil or a parachute. All of these are things that real spiders can do with the seven or eight types of silk for which they’re equipped. But could a spider use his silk to make baseball bats, trampolines, dummies, bandages and slings, or even watertight domes that would trap air so that he could breathe underwater?

Yeah, about that last one.

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Web Design

A friend recently asked me about what to do about the black widow that was spinning a web over her entire sliding glass back door. (When you are the naturalist among your friends, you tend to get a lot of extermination questions.) To be perfectly frank, I hate spiders. Whenever I make the conscious choice not to squash a spider on sight, I give myself a little mental cookie, much the way I do when I put an aluminum can in the recycling bin. Call it the Indiana Jones principle: You’re allowed to be creeped out by one type of animal. I don’t understand some people’s fear of snakes, but I can respect tolerate it. I know some bad-ass people who are afraid of rats. I love most animals. Just not spiders.

But I do love a well-spun spiderweb. A dew-dappled spiderweb early in the morning is a thing of supreme beauty, and the silk itself is an awe-inspiring substance. Normal spider silk has the tensile strength of steel, while the silk of the Darwin’s Bark Spider is ten times stronger than Kevlar. Most silk lines are only a few microns across, but if a spider could weave a strand the width of a pencil, that strand could conceivably stop a Boeing 747 in mid-flight. What’s more, spiders are capable of weaving up to 8 different kinds of silk from its spinneret glands: silk for draglines, silk for wrapping egg sacs, silk for wrapping prey, silk for parachutes, etc. And not every web is the classic “spiral orb;” webs are also designed as tubes, funnels, tangles, sheets, and domes.

However, the spider I want to focus on today is an orb-weaver, the Australian St. Andrew’s Cross spider, pictured above. Members of the Argiope family, such as the St. Andrew’s Cross, are often called “garden spiders,” or “writing spiders,” on account of their habit of decorating their webs with flourishes that sometimes resemble language. The name for these decorative markings are stabilimenta.


Argiope aurantia. Don’t read too much into it.

At first glance, the “X” shaped stabilimentum of the St. Andrew’s Cross spider seems to have an obvious purpose: the make the spider’s silhouette less obvious to both predators and prey. But stabilimenta take many forms and shapes with spiders all over the world, and the reasons for them are legion, varied, and mysterious.

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Silent Island

When writing about the Lesser Short-Tailed Bat colonizing New Zealand 30 million years ago, I wrote it from the perspective of the bat. But no species can colonize an inhabited island peacefully. The bat might think of itself as a pilgrim, while the native birds consider it an invader. And as humans invade and colonize each other’s lands by caravan, ship, and airplane, a form of animal imperialism has followed us.

Guam is a South Pacific island that was, at one point, idyllic. We cannot know what the ecosystem of Guam looked like 4,000 years ago when it was first colonized by humans, but when the dust and blood settled over the millenia, those early pioneers forged a sort of peace accord with the island, and the ecosystem re-calibrated itself to accommodate them. These people became the Chamorro, a culture based on the principles of respect and reciprocity. They had a mythology, but no religion; ancestor veneration took the place of deity worship. (Although there is one 17th century account of human sacrifice.)

Then, in the 15th century, the Spanish invaded. To say nothing of the misery visited on the people, the island was invaded by the rats, pigs, dogs, chickens, deer, and water buffalo the Spaniards brought with them; an ecological blitzkrieg. When control of Guam was passed to the U.S. after the Spanish-American War of 1898, we established a major naval base there (and introduced the poisonous and insatiable cane toad), which in turn was captured by the Japanese after Pearl Harbor. The Chamorro suffered torture, beheadings, and rape under Japanese occupation, and the island suffered the Giant African Snail which devastated the island’s crops. This is not to mention all of the invasive plants and pathogens introduced, which starved the local wildlife and pushed out the native vegetation. Then, in the 1950’s, when the island was again under the stars & stripes, we struck what could be the finishing blow.

This is the Guam Micronesian Kingfisher. No picture I could find could do justice to the magnificent plumage of this bird, which I have seen at the National Zoo in Washington, D.C. It behaves very much like North America’s belted kingfisher: furtive, with a raspy, laughing call, and specialized for diving into the water to catch small fish. It was once found all over the island. Now the kingfisher, like most of the birds on Guam, is extinct in the wild, the victim of American imperialism and a little brown snake.

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The Mystery of the Glow-In-The-Dark Scorpion

Here is a biological riddle that’s been fascinating me lately. While scorpions are not a “rare” animal, per se, they possess a trait that has yet to be fully explained by evolutionary science: they glow under ultraviolet light.

This isn’t bioluminescence. They are not generating their own light. Only under a source of ultraviolet, like a blacklight, do they show their true colors. But scorpions are nocturnal and stay out of the sun… and raves in the desert, while apparently not uncommon, aren’t exactly natural. So why would scorpions evolve the ability to glow when they don’t seem to use it? After the jump, some hypotheses, and why they are probably wrong.

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The Spider That Plays The Guitar

Part III of the Rock and Roll series: This one is for guitarists and vocalists. The subject: AMPLIFICATION.

Africa’s Namib Desert is one of the harshest and most unforgiving environments on Earth. Located off the aptly-named Skeleton Coast, it has the lowest annual rainfall of any place besides Antarctica. If you were shipwrecked there, you wouldn’t find drinkable water, but every morning you’d be treated to a tantalizing fog that rolls in from the ocean and quickly evaporates in the hot desert wind.

Because of the wind and the fog, it’s useless for native spiders to spin webs. So the Corolla Spider has a different strategy. It makes a burrow, and surrounds it with quartz pebbles.

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