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| European Garden (Cross) Spider - Araneus diadematus | |
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| Tweet Topic Started: Jul 6 2013, 04:00 PM (3,238 Views) | |
| Taipan | Jul 6 2013, 04:00 PM Post #1 |
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European Garden (Cross) Spider - Araneus diadematus![]() Scientific classification Kingdom: Animalia Phylum: Arthropoda Class: Arachnida Order: Araneae Suborder: Araneomorphae Family: Araneidae Genus: Araneus Species: Araneus diadematus The European garden spider, diadem spider, cross spider, or cross orbweaver (Araneus diadematus) is a common orb-weaver spider found in Europe and parts of North America, ![]() Range European garden spider (orb-weaver) varieties are very commonly found through-out Europe and North America. In America, their range extends from New England and the Southeast to California and the Northwestern United States. They can also be found in parts of southern Canada adjacent to the United States. ![]() Size and markings Individual spiders' colouring can range from extremely light yellow to very dark grey, but all European garden spiders have mottled markings across the back, with five or more large, white dots forming a cross. The white dots result from cells filled with guanine, which is a byproduct of protein metabolism. Adult females range in length from 6.5 to 20 mm (0.26 to 0.79 in), while males range from 5.5 to 13 mm (0.22 to 0.51 in). During mating, the much smaller male will approach the female cautiously. If not careful, he could end up being eaten by her (see video below). ![]() Male Garden Spider ![]() Female Garden Spider Specialization The third pair of legs of garden spiders are specialized for assisting in the spinning of orb webs. These spiders also use them to move around on their web without getting stuck. These legs are useful only in the web; while on the ground, these legs are of little value. Since this tends to be a passive animal, it is difficult to provoke to bite—but if it does, the bite is just slightly unpleasant and completely harmless to humans. ![]() The webs are built by the larger females who usually lie head down on the web, or in a nearby leaf (with a signal thread attached to a leg), waiting for prey to get entangled in the web. The prey is then quickly captured and wrapped in silk before being eaten. Orb spiders are said to eat their webs each night along with many of the small insects stuck to it. They have been observed doing this within a few minutes. A new web is then spun in the morning. ![]() |
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| Taipan | Jul 6 2013, 04:08 PM Post #2 |
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How Spiderweb's Shocking Charge Captures Prey By Tia Ghose, Staff Writer Date: 05 July 2013 Time: 07:20 AM ET ![]() The cross spider, Araneus diadematus, is a common orb-weaving spider found throughout Europe and North America. Spiders may trap unsuspecting prey by sucking them in using electrostatic attraction, new research suggests. The new study, published today (July 4) in the journal Scientific Reports, found that the spiderweb of the common cross spider (or garden spider) is attracted to electrically charged objects, with the sticky threads of spider silk arcing toward each other in response to a charged object. Stroke of inspiration Some flying insects, as they flap their wings, for instance, generate an electric charge. As such the new results suggest that charged bugs such as honeybees could be sucked into, and then trapped by, a spider's sticky web as they fly by. "Charged insects can produce a deformation of a spiderweb," said study co-author Victor Ortega-Jimenez, a biologist at the University of California, Berkeley. "Any insect that is flying very close to the spiderweb can be trapped by the electrostatic effect." Ortega-Jimenez noticed this phenomenon while playing with a simple toy with his daughter: an electrostatically charged "magic wand" that can cause objects such as paper to levitate. While doing so, they decided to charge up a few insects and even brought it near a spiderweb that was nearby, which deformed in response to the magic wand He also knew that honeybees generate an electric charge of up to 200 volts as they flap their wings, which may help them pick up pollen from negatively charged flowers. Several studies have revealed that spiderwebs can dramatically deform in response to prey. So he wondered whether spiderwebs could use electrostatic attraction to lure prey. Charging webs To find out, Ortega-Jimenez and his colleague Robert Dudley gathered spiderwebs of the cross spider (Araneus diadematus) from around the UC Berkeley campus. Back at the lab, they studied how the spiderwebs responded to electrically charged objects. They found that the web and positively charged objects were attracted to one another. What's more, the silk threads of the spiderweb curved toward each other underneath a charged honeybee that was falling toward it, making it likelier that the hapless insect would get entangled in the deadly web. The deformation was nearly half the length of the insects, a fairly big change. "This is quite intriguing," said Markus Buehler, a materials scientist who studies spider silk at the Massachusetts Institute of Technology, who was not involved in the study. "This attraction pulls the insect to the web and enhances the likelihood that it is being caught in the web." But it's not clear how often this strange effect plays out in nature. Cross spiders mostly dine on flies, not bees, and so far, no one has tested whether flies have an electric charge. The bigger question, Buehler said, is how many insects are electrically charged. http://www.livescience.com/37953-spiderweb-electrostatic-charge-traps-prey.html Spiderweb deformation induced by electrostatically charged insects Victor Manuel Ortega-Jimenez & Robert Dudley Scientific Reports 3, Article number: 2108 doi:10.1038/srep02108 ABSTRACT Capture success of spider webs has been associated with their microstructure, ornamentation, and wind-induced vibrations. Indirect evidence suggests that statically charged objects can attract silk thread, but web deformations induced by charged insects have not yet been described. Here, we show under laboratory conditions that electrostatically charged honeybees, green bottle flies, fruit flies, aphids, and also water drops falling near webs of cross-spiders (Araneus diadematus) induce rapid thread deformation that enhances the likelihood of physical contact, and thus of prey capture. http://www.nature.com/srep/2013/130704/srep02108/full/srep02108.html |
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| Taipan | Nov 5 2013, 05:10 PM Post #3 |
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Watch a Spider Amputate its Own Leg By Douglas Main, Staff Writer | November 04, 2013 01:48pm ET ![]() A European garden spider amputates its own leg, likely to prevent venom from a wasp bite entering the rest of its body. You know how it is. You've just killed a delicious wasp and are preparing to feast when, all of a sudden, you feel the pangs of venom rushing up your leg. So you bite it off. Or such was probably the case for a humble European garden spider filmed by Tim Edwards, an editor at BBC Earth, in his garden. Edwards notice that after wrapping up the wasp, the spider changed its behavior and appeared to stroke and bite one of its legs, before it fell off shortly later, according to the BBC. Edwards consulted biologists who said that the spider likely self-amputated (a process known at autotomy) to prevent venom from the wasp from reaching the rest of its body. Garden spiders are a common — but apparently bad-ass — arachnid found throughout Europe. Luckily, they regenerate legs after they periodically molt, or shed their skin. So this spider won't be doomed to a life with seven legs. http://www.livescience.com/40854-watch-spider-amputate-leg.html |
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| Taipan | Jun 6 2014, 05:53 PM Post #4 |
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Spiders Listen to Their Webs A spider's silk web is more than a home. It's also a stringed instrument. Carrie Arnold National Geographic PUBLISHED JUNE 5, 2014 When the early morning sun glints off droplets of dew on the gossamer strands of a spider web, it creates a visual masterpiece. Now scientists have found that an elaborate silk-woven web is also an acoustic tour de force. The silk can vibrate at a wide range of frequencies, which—when plucked—give the spider vital information about the state of its web and the presence of prey. "This study is fascinating," said Joyce Wong, a biomaterials scientist at Boston University and an avid cellist who was not involved with the study. "I've worked with spider silk for years, but I've never contemplated its sonic properties." This discovery, she said "has opened up a new line of research and applications that I hadn't thought about." Compensating for Poor Eyesight Spider silk has long fascinated scientists for its remarkable combination of strength and flexibility. Most man-made materials have one of these properties, but not the other. Eons of evolution have slowly tweaked the composition of spider silk to create a material that can absorb energy without being overly rigid. Spiders, however, don't care about high-tech applications of their silk. They weave their webs to catch prey and attract mates. But while humans can generally spot an insect trapped in a web, spiders—which have extremely poor eyesight—can't. Instead, they appear to rely on vibrations from the silk strands to locate prey and find deformities in the web. As a spider plucks and pulls on the web, sending out ripples in every direction, it can sense the vibrations in each of its eight legs. "They generate these vibrations to get information," said Beth Mortimer, a doctoral student in the Oxford Silk Group at Oxford University and the lead author of the recent study. "Because spiders have eight legs, they essentially have an ear covering all different directions." Mortimer's latest work, published yesterday in Advanced Materials, shows how spider silk can transmit such detailed information. ![]() Scientists fired a bullet at the spider silk to see how the material vibrated. Good Vibrations In their experiments, Mortimer and other researchers used single strands of silk obtained from two species of web-weaving spiders: Nephila edulis and Araneus diadematus. Spider silk from these representative species, they found, can vibrate at a much wider range of frequencies than many other natural and synthetic fibers. Imagine the strings on a violin, Mortimer says. "Each string can only be tuned to a few different notes. But a violin string made out of spider silk could be tuned to a tremendous range of different notes." To measure how spider silk vibrates, Mortimer and her colleagues took an unusual approach: They shined a laser on a piece of silk, then fired a bullet at it. Spiders determine how the silk vibrates using more prosaic methods. They create transverse waves by bouncing up and down on their web and longitudinal waves by plucking the strands of silk. Those waves alter the silk's vibrational frequency by tweaking the composition of the silk's proteins and by adjusting the tension of the silk in the web. Together, these techniques can help a spider pinpoint any damage to its webs—and any prey that might have become ensnared. And because spider silk can vibrate at so many frequencies, the spider can sense movements as small as a hundred nanometers—1/1000 the width of a human hair. Biology and Biomimicry Spiders have succeeded evolutionarily. The inherent variability in their silk is one of the major reasons why. It enables a spider to respond to a range of environmental conditions, such as humidity and high winds. Now that Mortimer and her colleagues have identified some of the vibrational properties of single strands of spider silk, they're working to determine how these may be altered as spiders weave their webs. Besides helping scientists better understand spider biology, that information may also help materials scientists engineer supersensory devices using spider silk, such as hearing aids. So the next time you see a beautifully woven spider web, remember you're only perceiving half of its beauty. The other half can only be felt. http://news.nationalgeographic.com/news/2014/06/140605-spiders-silk-webs-pluck-string-vibrations/ |
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