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| Hobo Spider - Tegenaria agrestis | |
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| Tweet Topic Started: Aug 1 2012, 01:28 AM (7,549 Views) | |
| Scalesofanubis | Aug 1 2012, 01:28 AM Post #1 |
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Omnivore
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Hobo Spider - Tegenaria agrestis![]() Scientific classification Kingdom: Animalia Phylum: Arthropoda Class: Arachnida Order: Araneae Family: Agelenidae Genus: Tegenaria Species: Tegenaria agrestis ![]() The hobo spider (Tegenaria agrestis) is a member of the genus of spiders known colloquially as funnel web spiders, but not to be confused with the Australian funnel-web spider. It is one of a small number of spiders in North America whose bites are generally considered to be medically significant. Individuals construct a funnel-shaped structure of silk sheeting and lie in wait at the small end of the funnel for prey insects to blunder onto their webs. Hobo spiders sometimes build their webs in or around human habitations. This species of spider has a reputation for aggressiveness, due to its poor eyesight. They will normally avoid contact with humans unless accidentally crushed or squeezed. The spider's venom is strong enough to cause considerable local pain and, possibly, necrosis. Native European Range Not Shown Habitat and History The hobo spider is native to Europe, where it is a resident of fields, rarely entering human habitations due to the presence of major competitors, particularly the giant house spider (Tegenaria duellica) which is a common resident of houses and other man-made structures in Europe. As a result human contacts with the hobo spider are uncommon in Europe. The species was first described in 1802 by naturalist C.A. Walkenaer, under the name Aranea agrestis, in reference to its western European habitat in fields, woods, and under rocks. Tegenaria agrestis is a non-native species in the United States, where it was introduced to the Pacific Northwest from Western Europe. It is believed to have first appeared in the port city of Seattle sometime before the 1930s. There is speculation that it arrived as eggs in commercial agricultural shipments from Europe, since isolated adults in shipments would have had difficulty in establishing a breeding population. It was first reported in the U.S. in 1936 by arachnologist Harriet Exline (as Tegenaria magnacava). There, without the widespread presence of any dominant competitors, it rapidly adapted to living in urban areas, where it became abundant and extended its range. By 1968 it had become established as far east as Spokane, Washington, and Moscow, Idaho, and as far south as Roseburg, Oregon. Two other closely related spiders live in Washington state, the giant house spider (Tegenaria duellica, or alternatively Tegenaria gigantea) and the barn funnel weaving spider or domestic house spider (Tegenaria domestica). All three of these spiders originated in Europe. ![]() Identification Spiders, including the hobo spider, vary considerably in appearance, and identification can be difficult. Identification relies on an examination of the spider’s anatomy. Positive identification requires microscopic examination of the epigynum and palps and is best done by an Arachnologist. However, the following characteristics can help in identification of hobo spiders in order to prevent misidentification and eradication of beneficial species with a similar general appearance. Hobo spiders lack the colored bands found on many spiders of the Agelenidae family where the leg joints meet. The abdomen has chevron (V-shaped) patterns (possibly many of them) down the middle, with the chevrons pointing towards the head. Like other funnel spiders, hobo spiders have two spinnerets extending from the bottom of the abdomen. Hobo spiders have a light stripe running down the middle of the sternum. If the spider instead has three or four pairs of light spots on the lateral portions of the sternum, then it is one of the other two related Tegenaria species. However absence of spots is not conclusive proof that the spider is a hobo spider, since the spots on other Tegenaria species may be extremely faint and not readily visible. Hobo spiders do not have two distinct longitudinal dark stripes on the top side of the cephalothorax, instead showing indistinct or diffused patterns. Washington spiders with distinct dark stripes include spiders from the genuses Agelenopsis and Hololena and possibly some wolf spiders. (These spiders do not have common names.) ![]() Toxicity and Aggression he toxicity and aggression of the hobo spider are currently disputed by arachnologists. One common name, the aggressive house spider may arise from a misinterpretation of the Latin name agrestis, (lit. "of the fields") as "aggressive". If a hobo spider is tending an egg sac, it may become aggressive if it perceives the egg sac as being threatened. However, they generally do not bite unless forced to protect themselves. In the United States, the hobo spider has been considered to be a dangerous species based on a toxicology study on rabbits where lesions appeared after spiders were induced to bite the rabbits. This laboratory study has led to the proposal that in some parts of the U.S. nearly all bites imputed to the brown recluse spider are in reality the hobo spider's bite. The CDC and other U.S. government agencies have also used this same study as the basis for a report claiming that the hobo spider bite causes necrosis in humans, despite the absence of any confirmed cases. Subsequent attempts to replicate the study by injecting sufficient venom to ensure envenomation have failed to produce necrotic lesions, and there is even question as to whether the lesions observed in the original study were necrotic. In Canada, there are scientists who claim that no hobo spider bites lead to dermal necrosis. Hobo spiders are common in Europe, though bites are relatively unknown, and there are no confirmed reports of them causing necrosis despite hundreds of years of coexistence there. The only documented case of a verified hobo spider bite leading to necrotic skin lesions involves a person who had a pre-existing medical condition (phlebitis) that can also cause the appearance of skin lesions. Hobo spider bites are not known to be fatal to healthy humans. The necrosis in purported cases is similar to, but milder than, that caused by the brown recluse spider, and in severe cases can take months to heal. Other reported symptoms include intense headaches, vision abnormalities, and/or general feelings of malaise. These symptoms are not confirmed for the hobo spider bite specifically due to lack of positive identification of the spider by an expert, and the Oregon Poison Center (affiliated with the Oregon Health & Science University) is attempting to gather definitive evidence regarding the validity of these reports as of September 2007.
Edited by Taipan, Aug 13 2012, 09:17 PM.
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| Taipan | Jan 17 2014, 01:34 PM Post #2 |
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Male Spiders Must Shake Abdomen — or Be Eaten By Stephanie Pappas, Senior Writer | January 16, 2014 07:01pm ET ![]() A black widow female dwarfs her male counterpart. Male black widow spiders shake their abdomens to avoid getting eaten by potential mates. The vibrations caused by the male spider's shaking travel along the females' webs, alerting the females to the presence of a potential mate, a new study finds. The vibrations are very different from the staccato, sporadic movements caused by ensnared prey. "They take a few steps and then they stop and vibrate their abdomen, and then they take a few steps and vibrate again," study researcher Samantha Vibert, a doctoral candidate at Simon Fraser University in Canada, said of the males. Vibert and her colleagues reported their findings today (Jan. 16) in the journal Frontiers in Zoology. Shaking males Spiders use their webs as extensions of their own bodies, able to sense vibrations on the threads that trigger their response to prey. But when an arachnid gentleman caller comes along, he runs the risk of being mistaken for a delicious moth and attacked. Vibert knew from observing hobo spiders (Tegenaria agrestisi) that mating spiders perform elaborate dances. She wanted to know what was behind these complex displays. To find out, she and her colleagues investigated two web-dwelling spiders, the western black widow (Latrodectus Hesperus) and the hobo spider. Hobo spiders produce sheet webs, whose familiar, organized patterns usually come to mind when people think of spiderwebs. Black widows produce tangle webs, which look like cobwebs. First, the researchers recorded vibrations of male spiders venturing onto females' webs as well as the vibrations made when a house fly or house cricket got trapped by the sticky silk. The researchers then compared the vibrations' duration, frequency and amplitude. They found that prey and potential mates make very different vibrations. The male spiders produced continuous, long-duration vibrations with low amplitudes, meaning that they were "quiet" compared to the sporadic, percussive vibrations made by trapped prey. The differences were especially pronounced in black widow spiders, Vibert told LiveScience. Male black widows produced these good vibes by moving their abdomens in a rapid motion — reminiscent of twerking. Good vibrations Next, the researchers played recorded vibrations onto webs occupied by females. The scientists tested vibrations from both prey and male spiders, played on either high or low, and watched how the females responded. "It didn't really matter what the vibration sounded like, but it had to be quiet," Vibert said. "If you play back a very quiet, whisperlike vibration, then the females did not respond aggressively." Strong vibrations sent the female spiders scurrying over in attack mode. But little whispers simply got their attention — some turned toward the source of the vibrations, and some even responded with abdominal twitches of their own, suggesting back-and-forth communication. That wouldn't be the only amazing trick spiders can play with their webs. On Jan. 8, a YouTube video revealed the magic of the slingshot spider (probably a species called Naatlo splendida), which actually flings its entire web at potential prey. Still, it's the communication aspect that amazes Vibert. "I think what really blew my mind was just how complex their signaling system is," she said. Courting spiders often show off with graceful dances, bobbing, weaving and circling around their intended mate, Vibert said. "Spiders can be really beautiful, and they're a lot more complex than most people give them credit for," Vibert said. "If you go past the spider fear, the phobia, there are really quite a lot of things that will make you smile." - See more at: http://www.livescience.com/42653-spider-mating-twerking.html#sthash.3uy3d50S.dpuf Journal Reference A meal or a male: the 'whispers' of black widow males do not trigger a predatory response in females Samantha Vibert, Catherine Scott and Gerhard Gries Frontiers in Zoology 2014, 11:4 doi:10.1186/PREACCEPT-3560191391041684 http://www.frontiersinzoology.com/content/11/1/4/abstract |
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