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What’s your first reaction when you see this picture? Love? Fear? Repulsion? If you are like many Americans, when you come across a spider, especially a large, hairy one like this tarantula, the emotions you experience are most likely in the realm of fear or disgust. Your actions probably include screaming, trapping, swatting, or squashing of the spider.

The post Spiders: the allure and fear of our eight-legged friends appeared first on OUPblog.

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By Rainer Foelix

Spiders are not exactly renowned for being colorful animals. Admittedly, most of the more than 40,000 spider species are rather drab looking. However, there are certainly several hundred species which are lively colored, e. g. bright red or bright green, and some are very colorful indeed. For instance, the so-called “peacock-spider” that shows a wide range of iridescent blue and green color hues, reminiscent of the plumage of peacocks or humming birds.

How do those colors in spiders come about?  Usually they are due to certain pigments deposited in the cuticle of their exo-skeleton or the underlying epidermis cells. Some spiders appear bright green or red or yellow, due to pigment granules. Other spiders contain crystalline deposits of guanine and strongly reflect the incoming light, either pure white or bright silvery. And often coloration is not really caused by pigments but is due to a special light diffraction (interference) in their cuticle. A very fine lamellation in the nanometer range causes a shift of the wavelength of the incoming light and thus a whole spectrum of colors  appears in the outgoing light. We all know this phenomenon from other natural objects such as mother-of-pearl, butterfly wings, or bird feathers. In spiders, such iridescent colors have been known for a long time but only in the last few years were they studied in detail.



• Figure One

   

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  A small crab spider (Diaea), mostly green, but with a red abdomen.

• Figure Two

   

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  Abdomen of a jumping spider (Phidippus) with red hairs and black scales.

• Figure Three

   

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  Male jumping spider (Phidippus) with iridescent green chelicerae.

• Figure Four

   

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  Leg segments of a tarantula (Poecilotheria) with blue and yellow hairs.

• Figure Five

   

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  Blue hairs of a tarantula (Poecilotheria) undr the electron microscope. The ridges of the hair shaft (left) consist of a fine cuticular meshwork (right) that causes the iridescence of these hairs.

• Figure Six

   

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  Peacock spiders (Maratus sp.) are among the most colorful jumping spiders. Most colors originate from iridescent hairs or scales.

Among the jumping spiders are some species where the mouth parts (chelicerae) are strongly iridescent: reddish-purple in the females and blue-green in the males. In that case it is the layering of the cheliceral cuticle that is responsible for the brilliant coloration. In some other species these interference colors reside entirely in hairs or scales of the body. This is for instance the case in those most colorful peacock spiders, where some scales change from blue over turquoise to green, and others from yellow to purple and golden. Under the electron microscope  those hairs and scales exhibit  a meshwork of thin layers that ultimately produces these structural colors. These shiny colors are much more pronounced in males than in females (as in most birds) and it is very likely that they play a crucial role in the visual courtship dances that the male performs in front of a female.

Somewhat surprisingly, such iridescent colors also occur in the large tarantulas. Several species are deep blue  and they are in high esteem (and highly priced!) among tarantula keepers. Some species may have additionally bright yellow hairs on their legs or golden-green hairs on their abdomen. Since most tarantulas are active at night, it is a bit puzzling why they are colorful at all. Their courtship is not visual but tactile, and no predator would be warned by bright colors that can only be seen under day light. So, it may well be that there is no specific purpose for having conspicuous colors, at least not in tarantulas. Perhaps the situation is comparable to colorful organisms living in the dark abyss of the oceans, in which colors only show up under illumination.

Since 14 March is Save-a-Spider-Day, let these colorful spiders brighten your day, or, as the old English saying goes: “If you want to live and thrive, let a spider run alive.”

Rainer Foelix is recognized as an authority on spiders. He studied Biology in both Germany and Switzerland and earned his PhD in Zoology. His is also the author of Biology of Spiders, now in its third edition.

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Image Credit: Figures one, two, three, and four by B. Erb. Figures five and six by R. Foelix

The post Colorful spiders? appeared first on OUPblog.

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Spiders

Right now I'm working on a book of my adult short stories called, Short Stories and Other Imaginings For The Reading Spot. Some pictures will be sketching and some in shades of gray, (not fifty shades!) This one is for a story called Spiders, a short short, about two paragraphs long. In the story the woman is working an apple press while she thinks about the things that are happening in her life.

 

sketch for Janoose & The Fall feather Fair

Another project I'm doing sketches for is a sequel for my children's book, Janoose The Goose  called, Janoose & The Fall Feather Fair. The Fox returns to Free Range Farm and he wants something from Janoose!
This book I co-wrote with my grandson. It's in the sketching stage as you can see by the picture. Hope you will come back to see how these two projects progress.
Thanks, JD

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So says Rilla. Her father does not approve. Her father is not a fan of tarantulas.

But he’ll forgive me, because he knew what he was getting into when he married me—the runaway train of my enthusiasm. How did we get on to spiders this morning? Rose said something about liking them; I think that was it. Beanie shuddered; she sides with her daddy on this one. Rose and I had a sudden impulse to go outside and see how many different kinds of spider we could count. Oddly, the pickings were slim: we only found two. Usually, they’re everywhere you look, causing some small child or other to shriek and run away. But there were two tiny ones of a species we’ve yet to identify, teensy oblong things with thin stripes of brown and tan, poised on webs stretched between the stems of the rose bush. Look, said Rose, I found this out yesterday: if you put a bit of twig in the web, the spider will come and snip it out. We waited, but the spider was on to us, frozen, silently glaring. Ten minutes later, after we’d roamed the yard in search of others, the twig was gone.

By chance—or maybe this is what put spiders on Rose’s mind this morning?—I’d pulled Fabre’s Life of the Spider off the shelf a day or two ago, thinking it might make a nice nature-study read for the summer, and added it to the high-tide stack in the living room. At the time, I wasn’t at all sure it would grab my girls—read-alouds are a challenge, these days, with one sweet boy endlessly butting in with questions, and the other impish one endlessly butting you with his head. But they were interested, so I gave it a try. Note to writers: If you want to hook an audience of 6-13-year-olds, “Chapter 1, The Black-Bellied Tarantula” is a sure-fire way to begin.

The Spider has a bad name: to most of us, she represents an odious, noxious animal, which every one hastens to crush under foot. Against this summary verdict the observer sets the beast’s industry, its talent as a weaver, its wiliness in the chase, its tragic nuptials and other characteristics of great interest. Yes, the Spider is well worth studying, apart from any scientific reasons; but she is said to be poisonous and that is her crime and the primary cause of the repugnance wherewith she inspires us. Poisonous, I agree, if by that we understand that the animal is armed with two fangs which cause the immediate death of the little victims which it catches; but there is a wide difference between killing a Midge and harming a man. However immediate in its effects upon the insect entangled in the fatal web, the Spider’s poison is not serious for us and causes less inconvenience than a Gnat-bite. That, at least, is what we can safely say as regards the great majority of the Spiders of our regions.

Nevertheless, a few are to be feared; and foremost among these is the Malmignatte, the terror of the Corsican peasantry. I have seen her settle in the furrows, lay out her web and rush boldly at insects larger than herself; I have admired her garb of black velvet speckled with carmine-red; above all, I have heard most disquieting stories told about her. Around Ajaccio and Bonifacio, her bite is reputed very dangerous, sometimes mortal.

Well played, Monsieur Fabre.

Of course we had to look up these twin terrors, the malmignatte with her thirteen red spots, and the tarantula, about whom Fabre’s predecessor, Leon Dufour, waxes quite lyrical: “…when I was hunting her, I used to see those eyes gleaming like diamonds, bright as a cat’s eyes in the dark.” Off we trotted to Wikipedia, for pictures, and YouTube, for pictures that move.