Spider

Template:Taxobox begin Template:Taxobox image Template:Taxobox begin placement Template:Taxobox regnum entry Template:Taxobox phylum entry Template:Taxobox classis entry Template:Taxobox ordo entry
Clerck, 1757 Template:Taxobox end placement Template:Taxobox section subdivision Araneomorphae
Mesothelae
Mygalomorphae
See the taxonomy section for families Template:Taxobox end

Spiders are invertebrate animal(s) that produce silk, have eight legs and no wings. More precisely, a spider is any member of the arachnid order Araneae, an order divided into two sub-orders: the Opisthothelae (which include the infraorders Mygalomorphae (trapdoor and tarantula spiders) and Araneomorphae (the modern spiders)) and the Mesothelae, which contains the Family Liphistiidae, burrowing spiders from Asia. The study of spiders is known as arachnology.

Many spiders hunt by building webs to trap insects. These webs are made of spider silk, a thin, strong protein strand extruded by the spider from spinnerets most coomonly found on the end of the abdomen. All spiders produce silk, although not all use it to spin elaborate traps. Silk can be used to aid in climbing, forming smooth walls for burrows, building egg sacs, wrapping prey, temporarily holding sperm and for many other applications.

Morphology and development

Spiders, unlike insects, have only two body segments instead of three; a fused head and thorax (called a cephalothorax or prosoma) and an abdomen (called the opisthosoma), supported by an exoskeleton composed mainly of chitin.

Spiders also have eight legs (insects have six), no antennae, and their eyes are single lenses rather than compound eyes. Additionally spiders have pedipalps (or just palps), at the base of which are coxae or maxillae next to their mouth that aid in maasticating food; the ends of the palp are modified in adult males into elaborate and often species specific structures used for mating.

Respiration and circulation

Spiders have an open circulatory system, meaning they don't have true blood or veins for it to travel in. Rather, their bodies are filled with haemolymph, which is pumped through arteries by a heart into spaces called sinuses surrounding their organs.

Spiders have developed several different respiratory anatomies, based either on book lungs, a tracheal system, or both. Primitive mygalomorph spiders generally have only a pair of book lungs filled with haemolymph, where openings on the ventral surface of the abdomen allows air to enter and diffuse oxygen. Modern araneomorph spiders often have a single book lung in addition to spiracles which deliver air into the tracheae, where oxygen is then diffused into the haemolymph. In the tracheal system oxygen interchange is much more efficient, enabling cursorial hunting (hunting involving rapid pursuit) and other advanced characteristics.

Vision

Spiders usually have eight eyes in various arrangements, a fact which is used to taxonomically classify different species. Sometimes one pair of eyes is better developed than the rest, or there are only six pairs, or no eyes at all. Several families of hunting spiders have developed good to excellent vision, such as wolf spiders and jumping spiders. However, most spiders that lurk on flowers, webs and other fixed locations waiting for prey have very poor eyesight, but possess extreme sensitivity to vibrations for hunting.

Defense

Some tarantula have a patch of urticating hairs on their abdomens for defense, which are generally absent on modern spiders and Mesothelae. Certain other species have specialized defense tactics. For example, the Golden Wheeling spider of the desert escapes Tarantula Wasps (a species of wasp that lays its eggs in a paralyzed spider so the larvae have enough food when they hatch) by flipping onto its side and cartwheeling away.

Life cycle

The spider life cycle progresses through three stages: the embryonic, the larval, and the nympho-imaginal (Foelix, 1996).

Between the time an egg is fertilized and the spider begins to take the shape of a spider is referred to as the embryonic stage (Foelix, 1996). As the spider begins to look more like a spider it enters the larval stage (Foelix, 1996). It enters the larval stage as a prelarva and, through subsequent molts, it reaches its larval form, a spider-looking, non self-sufficient animal feeding off its yolk supply (Foelix, 1996). After a few more molts, also called instars, body structures become differentiated; all organ systems are complete and the animal begins to hunt on its own; it has reached the nympho-imaginal stage (Foelix, 1996). This stage is differentiated by two sub-stages: the nymph, or juvenile stage and the imago, or adult stage (Foelix, 1996). A spider does not transition from the nymph to the imago until it has become sexually mature (Foelix, 1996). Once a spider has reached the imago stage, it will remain there until its death. Many spiders may live only about a year, but a number will live two years or more, overwintering in sheltered areas (the annual influx of 'outdoor' spiders into houses in the fall is due to this search for a nice warm place to spend the winter).

Reproduction

Spiders reproduce by eggs laid in silk bundles called egg sacs.

Spiders often use elaborate mating rituals (especially in the visually advanced jumping spiders) 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.

Sperm transmission is an indirect process. When a male is ready to mate, he will spin a web pad onto which the sperm is discharged. He then dips his palps (also known as 'palpi'), the small, leg-like appendages on the front of his cephalothorax, into the sperm, picking it up by capillary attraction. Mature male spiders have swollen bulbs on the end of their palps for this purpose, and this is a useful way to identify the sex of a spider in the field. With his palps thus 'charged' he then goes off in search of a female. The act of copulation occurs when the male inserts one or both palps into the female's genital opening, known as the epigyne. He transfers his sperm into the female by expanding the sinuses in his palp.

Very unusual behaviour is seen in spiders of the genus Tidarren, as the male amputates one of his palps before maturation and enters his adult life with one palp only. The palpi constitute 20% of its body mass, and since this weight greatly impedes its movement, the spider detaches one of the two to gain mobility. In the Yemeni species Tidarren argo, the remaining palp is then torn off by the female. The separated palp remains attached to the female's epigynum for about four hours and apparently continues to function independently. In the meantime the female feeds on the palpless male. (Journal of Zoology (2001), 254:449-459 Cambridge University Press doi:10.1017/S0952836901000954)

Do female spiders eat their mates?

It is often said that the male (usually significantly smaller than the female, down to 1% of her size for Tidarren sisyphoides), is likely to be killed by the female after the coupling, or sometimes before intercourse has occurred. This supposed propensity is what gave the Black Widow Spider, Latrodectus mactans its name. However, the three species of North American black widows do not seem usually to kill the male (although they may) and males can sometimes live in the web of a female for a while without being harmed. The male Australian Redback Latrodectus hasselti is killed ritually by the females after it inserts its second palpus in the female genital opening; in over 60% of cases the female then eats the male. Although the male Latrodectus hasselti (know also as the Australian redback spider) certainly die s during mating without the female consuming it, this species represents a possible strategy of "male sacrifice". The male redback, while copulating, 'somersaults' and twists its abdomen directly onto the fangs of its mate. Most males get consumed at this stage (Andrade 2003 reports 65%). Males that 'sacrifice' themselves gain the benefit of increasing thier paternity relative to males who do not get cannibalized (see Andrade 2003, Behavioral Ecology vol.14:531-538).

However, despite these examples, and many other similar reports, the story of the 'sacrificial male' might have become greater than the truth. Mating of spiders is not invariably followed by cannibalism. Rainer F. Foelix, (1982), says "The supposed aggressiveness of the female spider towards the male is largely a myth... only in some exceptional cases does the male fall victim to the female.". Michael Roberts (1995) says "It is rare for a fit male to be eaten by the female..." And yet, spider cannibalism does occur in some species more than in others, mainly species belonging to Latrodectus.

However, there has been speculation on why this sacrifice of male mates might occur at all. One theory is that once the male has mated, if he is unlikely to mate again then further extension of his life serves no evolutionary purpose, while the sacrifice of the male may help increase egg production through increased nutrition for the female. Having more offspring would give the male an advantage of having his genes passed on over other males that were not eaten. This would be consistent with the hypothesis (Roberts, 1995) that old or unfit males get eaten, whilst younger and fitter ones may survive to mate again. Another reason promoting male self-sacrifice could be low probabilities of finding anouther possible mate. Males of some spider species have mortality precentage of around 80% (for example L.hasselti from Andrade 2003, and other Latrodectus spp.). Thus investing more in a mate that has allready been found in order to increase paternity with that copulation, would increase the probability of transferring the males' genes to the next generation.

Ecology

Spiders have a great range of variation and lifestyle, although all are predatory.

While spiders are generalist predators, in actuality their different methods of prey capture often limits the type of prey taken. Thus web-building spiders rarely capture caterpillars and crab spiders that ambush prey in flowers capture more bees, butterflies and some flies than other insects. Groups of families that tend to take certain types of prey because of their prey capture methods are often called guilds. A few spiders are more specialized in their prey capture. Dysdera captures and eats sowbugs, pillbugs and beetles, while pirate spiders eat only other spiders. Bolas spiders in the family Araneidae use sex pheromone analogs to capture only the males of certain moth species. Despite their generally broad prey ranges spiders are one of the most important links in the regulation of the populations of insects. Every day on a meadow they devour over 10 g/m² of insects and other arthropods.

File:Goldensilkspider.jpg

A golden silk orb-weaver (Nephila clavipes), member of the family Tetragnathidae

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 as 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 foods. Many spiders will store prey temporarily. Web weaving spiders that have made a shroud of silk to quiet their envenomed prey's death struggles will generally leave them in these shrouds and then consume them at their leisure.

Spider webs and prey capture

Main article: Spider web

Some spiders spin funnel-shaped webs, others make sheet webs, and still others make the spiral "orb" webs which are most commonly associated with the order. These webs may be made with sticky capture silk, or with "fluffy" capture silk, depending on the type of spider. Webs may be in a vertical plane (most orb webs), a horizontal plane (sheet webs), or at any angle in between. Most commonly found in the sheet-web spider families, some webs will have loose, irregular tangles of silk above them. These serve to disorient and knock down flying insects, making them more vulnerable to being trapped in the web below. They may also help to protect the spider from aerial predators such as birds and wasps.

The spider, after spinning its web, will then wait on, or near, the web for a prey animal to become trapped. The spider can 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. For example, if a spider has chosen to wait along the outer edges of its web, it may spin a non-sticky prey or signal line to the web hub to monitor inter-web movement. The spiders have to be careful to only climb on the non-sticky strands.

The ability to spin webs allows a spider to catch prey without having to expend energy by running it down. Thus it is a very efficient method of gathering food. However, constructing the web is in itself an energetically costly process due to the large amount of protein required, in the form of silk. In addition, after a time the silk may lose its stickiness and thus become inefficient at capturing prey. It is not uncommon for spiders to eat their own web daily to recoup some of the energy used in spinning. The silk proteins are thus 'recycled'. The spider, in the middle of the web, also makes for a highly visible prey for birds and other predators. Many day-hunting orb-web spinners reduce this risk; for example, by hiding at the edge of the web with one foot on a signal line from the hub, or by appearing to be inedible or unappetizing.

The Net-casting spider balances the two methods of running and web-spinning in its feeding habits. This spider weaves a small net which it attaches to its front legs. It then lurks in wait for potential prey and, when such prey arrives, lunges forward to wrap its victim in the net, bite and paralyse it. Hence, this spider expends less energy catching prey than a primitive hunter such as the Wolf spider. It also avoids the energy loss of weaving a large orb-web.

Some spiders manage to use the 'signalling snare' technique of a web without spinning a web at all. Several types of water-dwelling spiders will rest their feet on the water's surface in much the same manner as an orb-web user. When an insect falls onto the water and is ensnared by surface tension, the spider can detect the vibrations and run out to capture the prey.

Types of spiders and the severity of their bites

Over 38,000 species of spiders have been identified, but because of their great ability for hiding, it is believed that about 200,000 species exist. All species are venomous (with the exception of the families Uloboridae and Heptthelidae), but only 40 species are known to be potentially deadly to humans.

Key to bite severity:

Extremely dangerous: Bite (assuming successful envenomation) may cause death in a healthy adult without emergency medical treatment.
Very dangerous: Bite may cause death in children, the elderly, the infirm without prompt medical treatment; and/or may cause debilitating injury. Prompt medical attention is required.
Dangerous: Bite unlikely to cause death/no known deaths reported; bite may cause significant local or systematic reaction. Medical attention is generally required to limit scope of symptoms.
Painful bites: Venom may inflict localized pain (similar to a bee sting) but does not have any dangerous or long-term side effects. Medical attention generally not required.
Not dangerous: Spider is unable to puncture human skin, and/or venom does not cause any significant reaction in humans.
No venom: This species does not produce venom. The only true Family of spiders in this category is the hackled orb-weavers; other Arachnids often confused with spiders, such as the harvestman, also do not produce venom.

A couple of things should be noted when considering the amount of danger posed by spider bites. First, it is often the case that a spider bite is "dry"--the skin may be pierced, but little or no venom injected into the victim; thus reducing or eliminating any harmful effects. Second, there have been reports of spider bites (by spiders considered otherwise harmless) causing allergic reactions in some individuals, up to and including anaphylactic shock, a life-threatening condition (much the same as a sting from an ant, bee, or wasp). Third, many spiders listed as dangerous are seldom encountered, or have dispositions that make them unlikely to bite despite the high toxicity of their venom. Finally, little is known about the toxicity of many spiders, due to infrequent encounters with Man; the list of venomous spiders is limited to those who are linked to medical events in humans or who otherwise have been extensively studied.

It should also be noted that for healthy adults, a bite by even the most toxic spiders on the list will require hours before death ensues; if timely appropriate emergency medicine is administered, victims should be expected to recover. The scenario given in movies such as Arachnophobia, where bite victims die within minutes, does not occur. One exception to this is with very small children; there is at least one recorded case of a small child dying within 15 minutes of a bite from a Sydney funnel-web spider; that occurred before the development of an antivenin.

Tangleweb spiders (Theridiidae)

Characterized by irregular, messy-looking, tangled, three-dimensional (non-sticky) webs, generally low and anchored to the ground or floor and wall. Commonly found in or near buildings; some build webs in bushes. The spider generally hangs in the center of the web, upside-down. Prey is generally ground-dwelling insects such as ants or crickets, in addition to small flying insects.

Widows (Latrodectus spp.) - a large, cosmopolitan group; all with relatively dangerous bites. These are relatively large (about the size of a nickel), 'burly-looking' house spiders; generally dark, often with a red mark on the glossy, smooth abdomen, either above or below. examples:

Black widow spider (very dangerous)
Latrodectus tredecimguttatus, known as the European or Mediterranean Black Widow, the Malmignatte spider, or the Karakurt spider (very dangerous)
Red-back spider (very dangerous)
Red Katipo and black katipo spiders (very dangerous)
Button spider (very dangerous)
Brown widow spider (dangerous; venom is less severe than the black widow)
Red widow spider (believed to be very dangerous; less is known about the effects of red widow envenomations on humans due to the limited range of this spider).

Steatoda--a large genus which includes the false black widows; these are sometimes mistaken for widows, but have more flattened abdomens, and abdominal markings are generally white stripes or dots rather than red dots. None of these is truly dangerous but some of them are medically significant:

S. grossa (possibly dangerous); bite resembles a very minor widow bite.
S. nobilis (painful bites)
S. paykulliana (painful bites)

others - the common "yuck!" spiders - large, globular abdomen, thin, spindly legs. Often rather non-descript patterns in gray or brown and white. examples:

American house spider (not dangerous)

Orb web spiders (Araneidae)

These spiders spin the familiar spiral snare that most people think of as the spider web. They range in size from quite large (6+ cm) to very small (<1 cm), but all are quite harmless to humans, beyond the shock entailed from walking into a face-height web and having a large spider dangling from your nose. Many of the day-time hunters have a 'ferocious' appearance, with spines or large 'fangs', but they are almost invariably inoffensive, preferring to drop on a drag-line to the ground when disturbed, rather than bite.

St Andrew's Cross spider (an Argiope) (not dangerous)
Long-jawed orb weaver Tetragnathidae (not dangerous)
Cyclosa conica (not dangerous)
Golden silk orb-weaver (not dangerous)
European garden spider (not dangerous)
Australian garden orb weaver spider (not dangerous)
Jewel Spider (not dangerous)
Spiny Micrathena (not dangerous)

Other forms of webs

This is a "catch-all" category, comprising members of several different groups that spin non-sticky webs in a variety of structural styles. Some (the Linyphiidae) make various forms of bowl- or dome-shaped web with or without a flat sheet or a tangled web above or below. Some make a flat platform extending from a funnel-shaped retreat, with generally a tangle of silk above the web. The common northern hemisphere 'funnel-web', 'house' or 'grass' spiders are only distantly related to the notorious Sydney funnel-web spider, and are generally considered to be quite harmless (with one notable exception - the Hobo spider, below). Some of the more primitive group Atypidae may make tubular webs up the base of trees, from inside which they bite insects that land on the webbing. These spiders look quite ferocious, but are not generally considered to be particularly dangerous to humans.

Sydney funnel-web spider (Atrax robustus) (extremely dangerous)
Bowl-and-doily spiders (Linyphiidae) (not dangerous)
Hobo spider (Tegenaria agrestis) (dangerous)
Grass spiders (Agelenidae) (not dangerous)
Filmy dome spider (Linyphiidae) (not dangerous)
Hackled orb-weaver (no venom)
Net-casting spider

Hunting spiders

Brazilian Wandering Spider (extremely dangerous)
Brown recluse spider (very dangerous)
Huntsman spiders (painful bites)
Jumping spiders (not dangerous)
Lynx spiders (not dangerous)
Nursery web spiders (not dangerous)
Spitting spiders (not dangerous)
Tarantulas (painful bites; some species like the Chinese bird spider may be dangerous)
Wolf spiders (Lycosidae) (not dangerous)
Yellow sac spider (painful bites - may produce effects like a milder form of Recluse venom)

Spiders which ambush their prey

This is another catch-all category that includes a diverse collection of spiders. Some actively lure prey (the Bolas spiders) and may capture them with a sticky ball of silk on a line; others wait in a high-traffic area and directly attack their prey from ambush.

Six-eyed sand spider (Sicariidae) (extremely dangerous)
Trapdoor spider (painful bites)
Crab spiders (Thomisidae) (not dangerous)
Bolas spiders (Araneidae) (not dangerous)

Others

Camel spider, not actually a spider at all, but rather a Solifugid (also commonly called Sun-spiders or Wind-scorpions). Very well-known as the source of many urban legends (no venom)
Kimura-gumo (Heptathela kimurai, a member of the Family Liphistiomorphae) (not dangerous)
Spruce-fir moss spider, Microhexura montivaga
Tooth cave spider, Neoleptoneta myopica
Bird Dropping Spider, Celaenia excavata

Spider bites

Most spiders are unlikely to bite humans because they do not identify humans as prey. Spiders, even small ones, may however bite humans 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.

Dangerous spiders in the United States include widow spiders, brown recluse spiders, hobo spiders, and yellow sac spiders.

None of these spiders will intentionally "come after you," but they should be removed from one's house to avoid accidental injury. Many authorities warn against spraying poisons indiscriminately to kill all spiders, because doing so may actually remove one of the biological controls against incursions of the more dangerous species by ridding them of their competition.

If dangerous spiders are 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.

Black widows

The Black widow spider is one of a number of widow spiders (genus Latrodectus) that carry a neurotoxic venom. Like many spiders, widows have very poor vision (jumping spiders and wolf spiders being notable exceptions), and they move with difficulty when not on their web. Widow spiders are large, strong-looking house spiders (but still have relatively spindly legs and deep, globular abdomens). The abdomen is dark and shiny, and has one or several red spots, either above or below. The spots may take the form of an hourglass, or two triangles, point-to-point. Male widows, like most spiders, are much smaller than the females, and may have a variety of streaks and spots on a browner, less globular abdomen. The males are generally considered to be much less dangerous (if at all) than the females. Widows tend to be quite non-aggressive, but will bite if the web is disturbed and the spider feels threatened. The venom, although rarely life-threatening, produces very painful effects including muscle spasms and 'tetanus-like' contractions. A serious bite will often require a short hospital stay. Children, elderly, and ill individuals are at most risk of serious effects.

Brown recluse spiders and hobo spiders

File:Brown recluse.jpg

Brown Recluse (Photo courtesy of the University of Nebraska)

Brown recluse spiders, (or "Violin Spiders" from the dark violin-shaped marking on the cephalothorax) Loxosceles reclusa, are slow-moving, retiring spiders which wander about in dim areas and under things, and so are more easily trapped against one's skin by clothing, bed sheets, etc. Even so, most encounters with this spider occur from moving boxes or rooting about in closets or under beds. The range of this spider in the US is approximately the lower 2/3 of the country by the eastern 3/4 of the country. A number of related Recluse spiders (some non-native introductions) are found in southern California and nearby areas, as well. The hobo spider, Tegenaria agrestis, may wander away from its web, especially in the fall, and thus come into contact with people and bite. This spider is found in the northwestern United States and throughout much of Europe. Oddly enough, in Europe it is considered a harmless outdoor relative of the common House Spider (Tegenaria domestica). The yellow sac spiders, Chiracanthum sp., take shelter in silk tubes during the daytime and generally come out to hunt at night. These pale yellow or whitish spiders are often found in houses at the top of walls, or wandering across ceilings. They are also commonly found outdoors on foliage. The drag-lines they leave while hunting are one of the most common "cob-webs" that are removed with broom and vacuum cleaner. People may unintentionally make contact with them in the dark and so be bitten. However, most people will live their entire lives in close proximity to them and never suffer a bite.

Brown recluse spider bites can produce very severe local symptoms, death of tissue around the wound, and, sometimes, severe systemic symptoms, including organ damage. The bites of hobo spiders and yellow sac spiders can cause both pain and necrosis (tissue death). Typically, all these bites are characterized by open, sore-like wounds that heal very slowly and may leave scarring. It has been suggested that steroid treatments may speed healing and reduce scarring.

It is believed that many spider bites which are attributed (often by physicians and other medical personnel) to the brown recluse are in fact caused by the hobo spider (if caused by a spider at all). Many brown recluse bites are reported in the U.S. west coast states (Washington, Oregon, and northern California) where populations of brown recluse spiders have not been found.

There are other species of spider in the genus Loxosceles which are found in southern California and other southwestern states; most of these species live in remote areas and are rarely encountered by humans. Bites of Loxosceles spiders found in South America are more serious in their consequences than their North American relatives.

Huntsman spiders

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. They frequently enter houses and hunt over the walls and ceilings where they may run rapidly for long distances without pausing. When they actually do bite people, the bites are very unpleasant, but these spiders are not regarded as dangerous. They are quite common in parts of Australia. Australian huntsman spiders are typically non-aggressive except when defending their nests or their young.

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.

Redback jumping spiders

Some people have reported being bitten by redback jumping spiders (Phidippus johnsoni). Most reports seem to be from California. These relatively large, alert jumping spiders have bright red abdomens (the females have a black stripe), and should be clearly visible. 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. One 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. Like most of the larger spiders, the consequences of a bite seem little different than a wasp or bee sting. Since they do not frequent human habitations it should ordinarily be easy to avoid unpleasant contact with them.

Brazilian wandering spiders and Australian venomous funnel-web spiders

The Brazilian wandering spider (a ctenid spider) and the Australian venomous spiders such as the Sydney funnel-web spider (a mygalomorph only distantly related to the araneomorph funnel-web spiders) frequently bite people and are regarded as among the most dangerous in the world. They are quite aggressive spiders, and are prone to biting when confronted, rather than running away. The Sydney funnel-web spider, a large, bulky, black spider, is restricted to a relatively small area around Sydney, Australia. It is unequivocally the most venomous spider in the world; although Phoneutria has the most neurologically active venom, it is delivered in amounts rarely large enough to cause deaths. There are other dangerous species of Atrax and Hadronyche related to this spider in surrounding parts of Australia, including Tasmania. The males in this case have somewhat more potent venom than females and they also wander, making them more likely to be encountered in summer. The Brazilian wandering spider is a large, brown spider rather like a North American Wolf spider in appearance. It, like several other more harmless spiders, may hitch a ride in clusters of bananas. As a result, any large spider appearing in a bunch of bananas should be treated with due care. Oddly, many of the bites of this species are dry bites and no venom is released. The spiders are as large as some small tarantulas and have fairly long fangs. While venom from either spider can be deadly to children and the infirm, since the development of antivenom to the venoms of both were developed (the funnel web spider in the mid-1980's and the wandering spider in 1996), no humans have died from their bites. Nevertheless, any large spider which makes a threat display (raising front legs, rearing back to display fangs) when encountered should be treated with caution - especially in areas where these two types of spiders may be expected.

Taxonomy

Suborder Mesothelae

Arthrolycosidae (primitive spiders)
Arthromygalidae (primitive spiders)
Liphistiidae (primitive burrowing spiders)
An orb-weaver spider

File:Florinda coccinea-b.jpg

Florinda coccinea (Blacktailed Red Sheetweaver)

Suborder [[Opisthothelae--60.226.82.243 11:01, 18 December 2005 (UTC)]] Infraorder Araneomorphae

Agelenidae (araneomorph funnel-web spiders)
Amaurobiidae (tangled nest spiders)
Anyphaenidae (anyphaenid sac spiders)
Araneidae (orb-weaving spiders)
Caponiidae (two-eyed spiders)
Clubionidae (sac spiders)
Corinnidae (corinnid sac spiders)
Ctenidae (wandering spiders)
Cybaeidae (water spiders)
Deinopidae (ogre-faced spiders)
Desidae (intertidal spiders)
Dictynidae (dictynid spiders)
Diguetidae (coneweb spiders)
Dysderidae (woodlouse hunter spiders)
Eresidae (velvet spiders)
Filistatidae (crevice weavers)
Gnaphosidae (ground spiders)
Hahniidae (dwarf sheet spiders)
Hersiliiidae (tree trunk spiders)
Hypochilidae (lampshade spiders)
Leptonetidae (leptonetid spiders)
Linyphiidae (sheet weavers or money spiders)
Liocranidae (liocranid sac spiders)
Lycosidae (wolf spiders)
Mimetidae (pirate spiders)
Miturgidae (long-legged sac spiders)
Nesticidae (scaffold web spiders)
Oecobiidae (wall spiders, six-exit tent spiders)
Oonopidae (oonopid spider)
Oxyopidae (lynx spiders)
Palpimanidae (palp-footed spiders)
Philodromidae (philodromid crab spiders)
Pholcidae (daddy long-legs spiders)
Pisauridae (nursery web spiders)
Plectreuridae (plectreurid spiders)
Salticidae (jumping spiders)
Scytodidae (spitting spiders)
Segestriidae (tube-dwelling spiders)
Selenopidae (wall crab spiders)
Sicariidae (recluse spiders)
Sparassidae (huntsman spiders)
Tengellidae (tengellid spiders)
Tetragnathidae (long jawed spiders)
Theridiidae (tangle web spiders)
Theridiosomatidae (ray spiders)
Thomisidae (crab spiders)
Titanoecidae (titanoecid spiders)
Uloboridae (hackled orb-weavers)
Zodariidae (ant spiders)
Zorocratidae (zorocratid spiders)
Zoropsidae (zoropsid spiders)

Infraorder Mygalomorphae

File:Atypus piceus D1079.jpg

An atypical tarantula (Atypus piceus)

Actinopodidae )[Mouse spider]]s)
Antrodiaetidae (folding trapdoor spiders)
Atypidae (atypical tarantulas)
Barychelidae (brush-footed trapdoor spiders)
Idiopidae (trapdoor spiders)
Ctenizidae (trapdoor spiders)
Cyrtaucheniidae (wafer trapdoor spiders)
Dipluridae (curtain-web tarantulas)
Hexathelidae (venomous funnel-web tarantulas)
Mecicobothriidae (dwarf tarantulas)
Microstigmatidae
Migidae
Nemesiidae
Paratropididae
Theraphosidae (tarantulas)

Symbolism

The spider symbolizes patience, for its hunting with web traps. Some fictional and mythological characters are related to spiders:

Arachne, a weaver turned spider in Greek mythology.
Kwaku Ananse, the West African trickster.
- Aunt Nancy, its American version
- Anansi the Spider is a superhero in the Static Shock animated series.
Spider-Man, the Marvel superhero with spider-like powers, and his avatars:
- Pavitr Prabhakar, his Indian version.
- Yu Komori, his manga version
Many techniques (fictional and otherwise) of ninja are named after spiders, usually due to involving spiderlike movement or other traits.

The Italian dance and music tarantella is related to tarantulas, either as a folk remedy for bites or from its vigorous movements.

References

The World of Spiders, by W. S. Bristowe Collins (New Naturalist), London 1958
The Life of the Spider, by John Crompton. Mentor, 1950.
How to Know the Spiders, by B. J. Kaston. Dubuque, 1953.
Biology of Spiders, by Rainer F. Foelix, 1982 and second edition, 1996
The Book of the Spider, by Paul Hillyard, Random House, New York 1994
Spiders, by Barbara York Main, Collins (The Australian Naturalist Library), Sydney 1976
Spiders of Britain and Northern Europe, by Michael J. Roberts, Collins, London 1995
Spiders of North America: an Identification Manual, by Darrell Ubick, Pierre Paquin, Paula E. Cushing, and Vincent Roth, American Arachnological Society 2005

Wise, David H. "Spiders in Ecological Webs." Cambridge University Press. Great Britain: 1993.

External links

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