Information about Spider
A spider is an invertebrate animal with eight legs. Spiders belong to the Long-jawed orb weaver, Family: Aranaedae. arachnid order Araneae, an Genus: Tetragnatha. order divided into three Scientific classification sub-orders in newer systems: Kingdom: Animalia the Mygalomorphae (the primitive spiders), the Phylum: Arthropoda Araneomorphae (the modern Class: Arachnida spiders) and the Mesothelae, which contains the Family Order: Araneae Liphistiidae, rarely seen Families burrowing spiders from Asia. Suborder Mesothelae Liphistiidae (primitive burrowing spiders) Many spiders hunt by Suborder Mygalomorphae building webs to trap Antrodiaetidae (folding trapdoor spiders) insects; these webs are made Atypidae (tarantulas) of spider silk extruded from Ctenizidae (trapdoor spiders) spinnerets on the end of the Dipluridae (tunnel spiders) abdomen, a thin, strong Theraphosidae (tarantulas) protein strand extruded by Mecicobothriidae (tarantulas) the spider. All spiders Suborder Araneomorphae produce silk, even those Filistatidae (crevice weavers) which do not spin elaborate Zoropsidae traps with them. Silk can be Eresidae (velvet spiders) used to aid in climbing, Dictynidae (leg fringe tangle web) forming smooth walls for Uroboridae (sector web spiders) burrows, coccooning prey, Amaurobiidae (tangled nest spiders) and for many other Dysderidae (woodlouse hunter) applications. Leptonetidae Sicariidae (recluse spiders) Lcidae (daddy long-legs spiders) Zodariidae (ground spiders) Palpimanidae (palp-footed spiders) Urocteidae (six-exit tent spider) Theridiidae (tangle web spiders) Nesticidae (scaffold web spiders) Linyphiidae (bowl-and-doily spiders) Micryphantidae (dwarf spiders) Tetragnathidae (long jawed spiders) Mimetidae (pirate spiders) Agelinidae (funnel-web spiders) Hahniidae (dwarf sheet spiders) Argyronetidae (water spiders) Pisauridae (nursery web spiders) Anatomy Lycosidae (wolf spiders) Oxyopidae (lynx spiders) Spiders, unlike insects, Gnaphosidae (sac spiders) have their bodies divided in Clubionidae (tube spiders) only two segments: prosoma Ctenidae (wandering spiders) or cephalothorax (a fused Thomisidae (crab spiders) head and thorax) and Salticidae (jumping spiders) abdomen. Some species, such Loxoscelidae (recluse spiders) as the Tarantula, have Scytodidae (spitting spiders) urticating hairs all over Dysderidae (cell spiders) their bodies. Spiders have Dictynidae (sievelike spinning plates) eight legs compared to the Uloboridae (weaves messy webs) insects' six, and their eyes Agelenidae (funnel-web spiders) (usually eight) are single Selenopidae (wall crab spiders) lenses rather than compound Sparassidae (huntsman, etc.) eyes like those that insects Miturgidae (long-legged sac spiders) have. Eyes can be arranged differently in different species. Sometimes one pair is better developed than the rest. Some species have a pair less or are even without eyes. While the various kinds of hunting spiders have good to excellent vision, the web weavers and the spiders that lurk on flowers and other fixed locations waiting for some insect to come their way would probably be considered legally blind if they were humans. This is very strange for a predator. How to hunt, if you're almost blind, deaf and you don't smell? The answer lies in their incredible sensitivity to vibrations. Insects have feelers but spiders don't. Instead, spiders have pedipalps, sometimes just called palps, which are two additional appendages next to their mouth parts that, besides having other functions, they use to help themselves manipulate the food that they eat. Spider blood does not circulate through vessels, it just fills the body of the spider. This is called an open circulatory system. Book lungs, respiratory organs with openings on the ventral surface of the abdomen, enrich the blood of some spiders with oxygen, and other spiders use spiracles. Some spiders use both. Reproduction Spiders reproduce by eggs laid in silk bundles called egg sacs, and the male (usually significantly smaller than the female) is likely to be killed by the female after the coupling, or sometimes before intercourse has occurred. This propensity is what gave the "black widow" spider (Latrodectus mactans) its name, and there has been much speculation on why this killing of male mates is so common, but it may simply be that female spiders tend not to discriminate between male spiders of their species and other similar small arthropods that are their normal prey. Spiders often use elaborate mating rituals to allow the male to approach close enough to inseminate the female without triggering a predatory response. Assuming that the approach signals are exchanged correctly, the male spider must make a timely departure after mating to escape before the female's normal predatory instincts come back into operation. Male spiders use modified palpi to convey seminal fluid to the genital passages of the female. When sexually mature, a male spider will spin a web pad onto which the contents of the abdomenal reproductive organs are discharged and then the seminal fluid is transferred into the cavities of the palpi; when an individual secures a mate he thrusts the palpi one at a time into her abdominal genital openings. Ecology Spiders have a great range of variation and lifestyle, although all are predatory. Spiders are the most important link in the regulation of the number of insects. Every day they devour over 100 kg on 1 hectare of a meadow. Predatory techniques There are many families of spiders, and the ways that they catch prey are diverse. But whether they catch insects, fish, small mammals, small birds, or some other small form of life, as soon as a spider makes contact with its prey it will attempt to bite. Spiders bite their prey, and occasionally animals that cause them pain or threaten them, to do two things. First, they inflict mechanical damage, which, in the case of a spider that is as large or larger than its prey, can be severe. Second, they can choose to inject venom through their hollow fangs. Many genera, such as the widow spiders, inject neurotoxins that can spread through the prey's entire body and interfere with vital body functions. Other genera inject venom that operates to produce tissue damage at the site of the bite. Genera such as that of the brown recluse spider produce a necrotoxin. The necrotoxin is injected into prey where it causes the degradation of cell membranes. In the larger victims that do not die from these attacks, painful lesions over a fairly wide area of the body can remain active for fairly long periods of time. Digestion is carried out internally and externally. The spiders secrete digestive fluids into their prey from a series of ducts perforating their jaws, These digestive fluids dissolve the prey's internal tissues.Then, the spider feeds by sucking the partially digested fluids out. Spiders consume only liquid food. Many spiders will store prey temporarily while this process of external digestion is going on. The prey of web weaving spiders that have made a shroud of silk to quiet their struggles while they are dying from envenomation will generally leave the prey in these shrouds and then consume them at their leisure. Spider webs Some spin funnel-shaped webs, others make irregular webs, and still others make the spiral "orb" webs which are most commonly associated with the order. The spider, after spinning its web, will then wait (often, but not always, at the center of the web) for a prey animal to become trapped. They sense the impact and struggle of a prey animal by vibrations transmitted along the web lines. Other species of spiders do not use webs for capturing prey directly, instead pouncing from concealment (e.g. Trapdoor spiders) or running them down in open chase (e.g. Wolf spiders). Spiders do not usually adhere to their own webs. However, they are not immune to their own glue. Some of the strands of the web are sticky, and others are not. The spiders have to be careful to only climb on the non-sticky strands. Spiders and humans Most spiders are unlikely to bite humans because they do not identify humans as prey. Spiders, even small spiders, may bite human beings when pinched. For instance, a common jumping spider (Family: Salticidae), around 3/8 inch (1 cm.) long, when pinched between the folds of a human's palm may inflict a bite that is about as painful as a bee sting. Normally, black widow bites are fatal only to children, due to the fact that children have much smaller body weights than adults and so the poison is more concentrated in their bodies when a bite does occur. There are several widow spiders, i.e., spiders of the genus Latrodectus, and they are generally regarded as all being about equally venomous. Unlike the other problematical spiders, the females of these most highly toxic of U.S. spiders stay on their web, and the males (which wander around seeking mates) are too small to deliver a dangerous amount of venom. So, "If you don't bother them, they won't bother you." Widow spiders are practically blind, and move with difficulty when they are not on their web. Brown recluse spiders frequently wander about and so are more easily trapped against one's skin by clothing, bed sheets, etc. The so-called "aggressive house spider" or hobo spider (Tegenaria agrestis) is also a wanderer that may come into contact with people and bite. The yellow sac spiders take shelter in silk tubes during the daytime and come out to hunt at night. People may unintentionally make contact with them in the dark and so be bitten. The bites of these four spiders may well require medical attention. The widow spiders, brown recluse spiders, hobo spiders, and yellow sac spiders are the dangerous ones among U.S. spiders.One other spider, the redback jumping spider (Phidippus johnsoni) can cause problems for humans if it is molested. Its bite can cause several days of swelling, tenderness, and pain at the bite site, Some people may also experience headaches, fever, chills, nausea, and vomiting.. None of these spiders will intentionally "come after you," but they should be removed from one's house to avoid accidental injury. Very serious consequences (especially for children), even death, can follow from widow spider bites. Brown recluse spider bites can produce very severe local symptoms, death of tissue around the wound, and, sometimes, severe systemic symptoms. The bites of hobo spiders can cause both pain and necrosis (tissue death), and yellow sac spider bites can be extremely painful. Outside of the U.S., the Brazilian Wandering Spider and the Sydney funnel-web spider frequently bite people and are regarded as among the most dangerous in the world. That being said, none of these spiders move into human territory with the intention of biting people. People blunder into them, and they defend themselves by biting. (There is one spider in California and Japan, probably a huntsman (tentatively identified as a member of the Sparassidae family, Heteropoda venatoria), that might run over and bite your finger if you touch the wall that it is clambering over. That behavior may well occur because its eyesight is good enough to see movement and general shape, but not sufficient to avoid mistaking something else for its natural prey. Many people regard the huntsman spiders as being singularly aggressive and fearless, but there is no record of their causing serious injuries to human beings. Huntsmen females are known as fierce protectors of their young, and will threaten and then possibly attack humans if they do not take the warning. Fortunately, while it would not be great fun to be bitten by one of these rather large spiders, they do not have or deserve a reputation like that of the black widow -- which is much less threatening looking.) Avoiding spider bites The website of the Carlsen Ranch asserts that almost half the black widow bites reported in the medical literature from 1901-1941 "were inflicted on the male genitalia by spiders on the underside of outdoor toilet seats." From the standpoint of a spider that likes to make its web under overturned wooden boxes resting on the ground, and in other such sheltered places near the ground, and which eats flies, an outdoor toilet is an almost ideal location. From the spider's point of view, it is in a large box about 2.5 feet tall, about 2 feet wide, and about five feet long. In the ceiling of this box there usually two holes about eight inches in diameter, through which a seemingly inexhaustible supply of houseflies enter. The spider will make its web at the top of this box and rest somewhere on or near the top of the box. If a black widow happens to be resting near the front edge of the hole when a male human visitor sits down, she may find herself pinned against the wood by his penis, and bite it. Black widow spider venom is a neurotoxin, and it has its ill effect on human beings by spreading from the site of the bite all over the victim's body. The severity of the effect is determined by two related factors: (1) the weight of the victim compared to the volume of poison injected (i.e., the concentration of the toxin in the victim's body), and (2) the speed with which the poison spreads through the body, since if it moves more slowly the body may be able to detoxify the venom before it causes a great deal of damage. Male genitalia have a very good blood supply, so a bite at such a location insures that the poison will spread rapidly to vital organs. Fortunately, in the United States there are currently very few such outdoor toilets, so the likelihood of getting a serious bite has greatly decreased since the early decades of the twentieth century, and such bites are no longer common. Although one source of trouble has been largely eliminated by indoor plumbing, chemical toilets, etc., the principle remains the same: Avoid putting your hands or other body parts where they will pinch or squeeze spiders. That means being very careful, if you live in black widow territory, of picking up things off the ground that have space underneath for a black widow web. If you find an overturned wooden or plastic carton, an abandoned pallet, or anything of that sort that could be the home of an industrious black widow, turn it over and have a look before you pick it up. If you find brown recluse spiders, hobo spiders, yellow sac spiders, or black widow spiders in your house or other buildings, it would be best to remove them. Many authorities warn against spraying poisons indiscriminately to kill all spiders, because doing so actually removes one of the biological controls against incursions of the more dangerous species. If one or more of the dangerous spiders is present in your area, then be mindful when you move cardboard boxes and other such objects that may have become the shelter of a poisonous spider. There is no need to be fearful, just do not grab a spider. The Sydney tunnel-web spider and the Brazilian wandering spider may be aggressive in defense of their nests. Fortunately the Sydney tunnel-web spider is restricted to a relatively small area around Sydney, Australia. The Brazilian wandering spider reportedly may hitch a ride in clusters of banannas. As a result, any large spider appearing in a bunch of bannanas may be one of these very toxic individuals, and should be treated with due care. Some people have reported being bitten by redback jumping spiders (Phidippus johnsoni). Most reports seem to be from California. These spiders have bright red abdomens (the females have a black stripe), and should be clearly visible even if they are not particularly large. It is unclear how the bites occur. Accidental contact seems rather unlikely since jumping spiders have excellent vision and could easily avoid being brushed by a human hand. It is also unlikely that they would mistake a human finger for their natural prey. Once source suggests that since they are quite attractive children may try to pick them up and in that way elicit a defensive bite. Fortunately, the worst consequences reported have been three to four days of discomfort, with no permanent damage. It may be that these spiders react aggressively to what they perceive to be attempts to capture them and may bite before they are pinched or squeezed by inquisitive humans. In any event, since they do not frequent human habitations it should ordinarily be easy to avoid unpleasant contact with them. The huntsman spiders have a worldwide reputation for scaring people. They are large, defend their nests, and may move toward people and make threat displays. When they actually do bite people, the bites are very unpleasant, but these spiders are not regarded as dangerous. Spiders, arranged by hunting method and common name Over 37,000 species of spiders have been identified but because of their great ability for hiding it is believed there are near 200,000 species. Almost all species are venomous, but only 30 species are known to be deadly dangerous. Spiders that live on tanglewebs: * Black widow spider (dangerous) * Golden silk spider (see below) (not dangerous) Spiders that live on orb webs: * St Andrew's Cross spider (argiope) (not dangerous) * Long-jawed Orb Weaver (see top) (not dangerous) * Cyclosa conica (not dangerous) Spiders that live in other forms of webs: * Sydney funnel-web spider (dangerous) * Bowl and doily spiders (not dangerous) * Hobo spider (dangerous) * Grass spiders (not dangerous) * Filmy dome spider (not dangerous) * Hackled orbweavers (no venom) Spiders that live on flowers: * Crab spiders (Thomisidae) (not dangerous) Spiders that live in shelters and rove around hunting: * Brazilian Wandering Spider (dangerous) * Brown recluse spider (dangerous) * Huntsman spiders (not dangerous) * Jumping spiders (not dangerous) * Lynx spiders (not dangerous) * Nursery web spiders (not dangerous) * Spitting spiders (not dangerous) * Tarantulas (not dangerous) * Wolf spiders (Lycosidae) (not dangerous) * Yellow sac spider (dangerous) Others: * Kimura-gumo (Liphistiomorphae) (not dangerous)
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