Poisonous spiders

Poisonous spiders (spiders having medically significant venom) exist in almost all parts of the world except those that are coldest. There is general agreement on which spiders give bites that may produce lasting damage or death, but not such general agreement on how one might sort spiders identified by genus and species in order of their threat to humans.

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.

As spiders do not prey on humans (or other large mammals), spiders do not "attack" people. Some spiders (including highly venomous species like the Brazilian wandering spider) will behave aggressively towards large animals and people that the spider perceives as a threat. Most spiders, however, prefer to avoid contact with humans and will flee from contact whenever they get the chance, biting only if they have no other choice. Many bites occur when a person steps on a spider, or inserts a limb into an article of clothing that the spider occupies. In some occasions, spiders may confuse a human being (or a part thereof) for prey; many bites by black widows in the past occurred in outhouses when the spider, nesting under the seat, mistook a human user of the privy for an insect meal. http://www.emedicinehealth.com/black_widow_spider_bite/page9_em.htm Emedicinehealth.com: Black widow spider bites

Concerned persons may wish to remove dangerous spiders from their homes, 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, 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.

Key to bite severity

The following key is used in this article as a rough indicator of bite severity:

Extremely dangerous: Bite (assuming successful envenomation) may cause death in healthy adults should they not receive emergency medical treatment.
Very dangerous: Bite may cause death or debilitating injury in children, the elderly, and the infirm providing that they do not receive prompt medical treatment.
Dangerous: Bite that is unlikely to cause death (generally few or no deaths have been reported); bites may cause significant local or systematic reactions. Medical attention is generally required to limit the 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 is generally not required.
Not dangerous: The spider is unable to puncture human skin, and/or its venom does not cause any significant reaction in humans.
No venom: Some species do not produce any 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.

Types of spiders with medically significant venom

The following types of spiders are known to have medically significant bites, with symptoms ranging from localized pain all the way to severe tissue destruction and potential death.

Brazilian wandering spiders (extremely dangerous)

The Brazilian wandering spider (a ctenid spider) is a large, brown spider rather like a North American Wolf spider in appearance. However, it has a highly toxic venom (one of the most neurologically active), and is regarded (along with the Australian venomous funnel-web spiders below) as among the most dangerous spiders in the world. 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 alleged to be dry bites and no venom is released but that claim is not definitive based on the margin of error when identifying the precise subspecies involved (assuming the spider body is saved or captured). In either case, the bite is at minimum mechanically painful due to the large size of the chelicerae (fangs) and considering the high levels of seretonin contained in the venom, the bite can be one of the most extruciating of all spider envenomations. The spiders are as large as some small tarantulas and as already mentioned, 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.

Australian venomous funnel-web spiders (extremely dangerous)

The Australian venomous funnel-web 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. Its venom contains a compound known as robustotoxin which is highly toxic to primates. Unlike the Brazilian wandering spider, which is alleged to occasionally deliver dry bites, these spiders typically deliver a full envenomation when they bite. 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.

Six eyed sand spiders (believed to be very dangerous)

The six-eyed sand spider, of southern Africa (and other spiders in the genus Sicarius), is considered by some to be the world's most venomous spider. Assays of its venom have led some to recognize this spider's bite as the most dangerous on record; and currently no antivenom exists for its bite. Fortunately, this specimen rarely interacts with humans, and is seldom known to bite; recorded envenomations by this spider are rare. A cousin of the recluse spider (and possessing the same toxic compound as found in recluse venom), this spider buries itself in the sand and strikes from ambush at prey that wanders too closely. Sand particles adhere to cuticles on its abdomen, thus acting as a natural camouflage if uncovered. If disturbed, it will run a short distance and bury itself again.

Mouse spiders (believed to be very dangerous)

The mouse spiders of the genus Missulena are a type of primitive burrowing spider found primarily in Australia. Several species of this genus are known to posess a venom which contains compounds similar to robustotoxin, the substance in funnel-web venom which is deadly to humans, and there have been several recorded bites by this spider producing severe symptoms requiring emergency medical treatment. However, unlike the funnel-web spiders, which have resulted in at least 13 deaths, there are no recorded human fatalities due to mouse spider bites, and many bites by this spider result in no serious complications. It is suspected that unlike Atrax and Hadronyche, which typically deliver full envenomations when they bite, that mouse spiders often give "dry" bites. When severe envenomation does occur, funnel-web antivenom has been shown to be effective.http://www.mja.com.au/public/issues/180_05_010304/isb10842_fm.html Geoffrey K. Ibister, "Mouse spider bites (Missulena spp) and their medical importance", Medical Journal of Australia 2004; 180 (5): 225-227

Widow spiders (very dangerous)

The widow spiders (genus Latrodectus), such as the black widow and red-back spider, are spiders 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.

Recluse spiders (very dangerous)

Recluse spiders (Loxosceles spp.), such as the brown recluse spider, also known as "violin spiders" or "fiddlers" from the dark violin-shaped marking on the cephalothorax, 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. The spiders will often creep along at a very slow pace and then make a sudden dart for a couple of inches, then return to the previous languid pace. Recluses are extremely venomous. Most encounters with this spider occur from moving boxes or rooting about in closets or under beds. The range of the brown recluse, L. reclusa 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.

Recluse spider bites can produce very severe local symptoms, necrosis of tissue around the wound, and, sometimes, severe systemic symptoms, including organ damage. 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.

Even more dangerous is the Chilean recluse, a species native to South America and found in many parts of the world, including in southern California and other southwestern states. Bites of this spider have been known to cause systemic reacions in 15% of reported cases, and fatalities in 3-4% of cases. http://bases.bireme.br/cgi-bin/wxislind.exe/iah/online/?IsisScript=iah/iah.xis&nextAction=lnk&base=MEDLINE_1966-1995&exprSearch=2577020&indexSearch=UI&lang=i Schenone H, Saavedra T, Rojas A, Villarroel F. "Loxoscelism in Chile. Epidemiologic, clinical and experimental studies". Revista do Instituto de Medicina Tropical de São Paulo 31:403-415, 1989

Hobo spiders (dangerous)

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).

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.

True tarantulas (some species dangerous)

The true tarantulas, of the family Theraphosidae, are fearsome looking spiders with somewhat notorious reputations. As large spiders, they have very powerful fangs and are capable of delivering a sizeable quantity of venom. However, many species of tarantula are known to be relatively harmless to humans. Tarantulas are typically divided between New World and Old World types; depending on what part of the world the spider in question comes from.

New world tarantulas (painful bites)

New World tarantulas--those indigenous to the Americas--have bites that generally pose little threat to humans (other than causing localized pain). The primary means of defense for these spiders are urticating hairs, which can cause irritation and other topical symptoms in humans. New World tarantulas are relatively docile, and are the type of tarantulas most frequently kept as pets

Old world tarantulas (some species dangerous)

Old World tarantulas, especially those indigenous to Asia, are another matter. These species lack urticating hairs, and use biting as a defensive mechanism (as well for subduing prey). In addition, these spiders are far less docile; and more likely to try and bite an adversary (including humans) if provoked. The effect of Old World tarantula venoms is not well studied, for the most part; however much anecdotal evidence suggests they have stronger venom than their New World counterparts.

One species whose venom has been studied extensively is the Chinese bird spider (Haplopelma spp.), a tarantula of the subfamily Ornithoctoninae. The venom has been found to contain numerous novel toxins, is effective at killing mice, and has been blamed for at least one fatality in China. However, there is little documented clinical evidence of the effects of this spiders' bite in humans; so firm conclusions about the level of danger posed by this spider cannot be drawn.

Yellow sac spiders (painful bites)

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 draglines 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.

False black widows (Steatoda--painful bites, minor systemic reactions)

The False black widow spiders (also known as false katipo, false button spider, cupboard spider, and in Australia, brown house spider) are spiders of the genus Steatoda which superficially resemble widow spiders. While the bite of Steatoda spiders are nowhere near as serious as that of true widow spiders, several of these spiders do have medically significant bites. The bite of Steatoda grossa, commonly known as the cupboard spider, is known to cause symptoms which have been described as a very minor widow bite; the medical community now refers to the symptoms of Steatoda bites as steatodism. Other spiders in this genus known to be problem biters include two chiefly European varieties, S. paykulliana and S. nobilis, and a species found mainly in New Zealand and South Afirca, S. capensis

Use of widow spider antivenom has been shown effective in treating steatodism. It should be noted that the genera Steatoda and Latrodectus are biologically close cousins; both beloning to the family Theridiidae. It should also be noted that there are over 100 species in this genus, but only several species have been associated with medically significant bites.

Members of this genus are characterized by the "D" shape of the cephalothorax, and the way the relatively straight line thus formed is mirrored by the blunt forward surface of the abdomen.They look something like this: Ə Other genera in this family generally have cephalothoraxes that are more oval in shape or even rather round, and that give the appearance of two body parts that are joined by a small connector.

Huntsman spiders (painful bites)

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), which 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. In general, however, members of this genus scramble wildly to escape when they become aware of a human moving into their vicinity.

Redback jumping spiders (painful bites)

Some people have reported being bitten by redback jumping spiders (Phidippus johnsoni). Many reports come from California,although their range is much wider and people elsewhere may have unpleasant contacts with them. These relatively large, alert but slow-moving jumping spiders have bright red abdomens (the females have a black stripe), and should be clearly visible. It is unclear how bites to humans occur. Accidental contact seems rather unlikely since jumping spiders have excellent vision and can 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. Since these spiders are quite large, their body length being around 12 mm (1/2 inch), the volume of their available venom is accordingly rather large. Fortunately, however, 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 from those of a wasp or bee sting. Since they do not frequent human habitations it should ordinarily be easy to avoid unpleasant contact with them.

Comparative analysis

It is often asked which type of spider is the most "dangerous" in the world. There isn't a simple answer to this question, as there are many things which must be taken into account 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 is injected into the victim. In such an instance, little or none of the spider's dangerous potential for harm is manifested.
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 may produce a harmful effect apart from the toxic quality of its venom).
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 their infrequent encounters with humans; the list of venomous spiders is limited to those that 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 may require hours before death ensues; if timely appropriate emergency medical treatment is administered, victims may 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 picture occurs because in the case of very small children the amount of venom dispersed throughout the body is many times the concentration in an adult. 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 event occurred before the development of an antivenin. Since the antivenin was developed there have been no fatalities due to this species.

The spiders believed to be most dangerous to humans, in terms of the risk posed by a bite, are the Sydney Funnel Web spiders and Brazilian Wandering Spiders. These spiders are potentially more dangerous than widow spiders because they have longer fangs and possess greater quantities of venom, thus they are capable of injecting far more venom to greater depths. Phoneutria nigriventer has approximately 2 mg of venom, but frequently gives dry bites or at least does not deliver all of its available venom. Atrax robustus has approximately 1.7 mg of venom. Bites of Six-eyed sand spiders are thought likely to be even more dangerous to humans than any of the others, but fortunately there have been no recorded cases of actual bites.

By general agreement, spiders of the genus Latrodectus (of which the Black Widow spider is the most notorious) kill more people per year, worldwide, than any other spider. Though their venom is extremely potent, these spiders are not especially large. Compared to many other species of spiders, their chelicerae are not very large. In the case of a mature female, the hollow, needle shaped part of each chelicera, the part that penetrates the skin, is approximately .1 mm (approx. .004 in) long, sufficiently long to inject the venom to a dangerous depth. The males, being much smaller, can inject far less venom and inject it far less deeply. The actual amount injected, even by a mature female, is very small in physical volume (.02–.03 mg). When this small amount of venom is diffused throughout the body of a healthy, mature human, it usually does not amount to a fatal dose. Deaths in healthy adults from Latrodectus bites are rare in terms of the number of bites per thousand people. Only sixty-three deaths were reported in the United States between 1950 and 1989 (Miller, 1992). On the other hand, the geographical range of the widow spiders is very great. As a result, far more people are exposed, worldwide, to widow bites than are exposed to bites of more dangerous spiders, so the highest number of deaths worldwide are caused by members of the genus Latrodectus. Widow spiders have more potent venom than most if not all spiders, and prior to the development of antivenom, 5% of bites result in fatalities.

This article is a work in progress. Standards, parameters reported, statistics available, etc., vary over the many nations of the world, so making accurate comparisons proves difficult. Suffice it to say for the present that bites given by spiders in the top row of photographs are extremely problematical because of their toxicity and the spiders' aggressive defense of themselves. The Widow spiders are nearly blind and will not respond aggressively. They will, however, give defensive bites if squeezed in any way. Within their more limited ranges, the other spiders in the top row of photographs are more likely to encounter humans because of their habit of wandering around in places frequented by humans.

Measurements

The LD-50 figures have limited utility since the effects of venoms differ widely from species to species. The University of California at Riverside reports that 5% of victims of widow spiders die, but comparable figures are not available for the other species. Before an antivenom was developed, deaths from Atrax and Hadronyche were very common. Some deaths from Phoneutria bites are reported, but much of their range is in the Amazon so reporting of bites may not be very complete.

Most LD-50 figures are based on experiments with laboratory mice. There are great differences in the sensitivities of various kinds of organisms to various kinds of venom. The relative sensitivities of mice to various venoms may not allow prediction of the exact degree of human sensitivity. So most of these figures can only give a rough approximation of the medical consequences of various spider bites to humans. Nevertheless, any venom capable of killing other organisms in small doses should be avoided by humans. A case in point are the Sicarius species. Their venom is extremely active in laboratory animals, but unknown in the case of humans.

Genus	Species	Common name	Body length	Venom amount	LD-50	Alternate LD-50	Deaths reported
Atrax	robustus	Venomous funnel-web	24–32 mm. http://spiders.ucr.edu/dermatol.html Vetter et al., UCR	0.25 mg (F) and 0.81 mg (M) http://www.inchem.org/documents/pims/animal/atrax.htm 2 mg http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=7207322&dopt=Abstract	.16 mg/kg http://www.arachnoboards.com/ab/archive/index.php/t-10093.html	unknown	1927–1980 13 deaths
Hadronyche	species	Venomous funnel-web	24–32 mm.	0.25 mg (F) and 0.81 mg (M) 2 mg	.16 mg/kg
Latrodectus	mactans	Black widow	8–15 mm	0.02–.03 mg. http://www.storysmith.net/Articles/Bites%20and%20stings.pdf Charles Stewart http://www.thudiv.com/variety/spider/spider1.htm) (Tung Hai University, Taiwan, article in Chinese)	0.002 mg/kg *	0.9 mg/kg	5% of reported bites prior to antivenom availability
Latrodectus	tredecimguttatus	Malmignatte	(approx. same)	(approx. same)	0.68 μg/kg http://homepage3.nifty.com/~hispider/spidervenom.txt (Ori and Ikeda)	16.25 μg/kg
Loxosceles	Reclusa	Brown recluse	1.2 cm (0.75 in) 6–10 mm	.13–.27 mg. http://www.scielo.br/scielo.php?script=sci_arttext&pid=S1678-91992003000200004 Manzoli-Palma			(rare)
Loxosceles	intermedia				0.48 mg/kg http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=9196551&dopt=Abstract		unknown
Loxosceles	laeta	Chilean recluse			1.45 mg/kg
Loxosceles	gaucho				0.74 mg/kg
Phoneutria	bahiensis	Brazilian wandering spider	30 mm	1.079 mg http://www.medscape.com/medline/abstract/12368110 (Free registration required.)	.00061–.00157 mg/kg
Phoneutria	boliviensis	Brazilian wandering spider	30 mm	1.079 mg.	.00061–.00157 mg/kg
Phoneutria	fera	Brazilian wandering spider	30 mm	1.079 mg	.00061–.00157 mg/kg		occasional death
Phoneutria	nigriventer	Brazilian wandering spider	3–5 cm (1.25–2 in) http://www.minaxtarantulas.net/artiklar/phoneutria/phoneutria_e.html Lelle Petterson	2.15 mg 1.079 mg.	15.20 ng/mg .00061–.00157 mg/kg	200 µg/kg (0.2 ng/mg) http://www.scielo.br/scielo.php?script=sci_arttext&pid=S1678-91992003000200004 (M. F. Manzoli-Palma, N. GobbiI, M. S. Palma)	unknown
Phoneutria	reidyi	Brazilian wandering spider	30 mm		.00061–.00157 mg/kg	0.3 mg/kg
Sicarius	(Africa & S.A. species)	Six-eyed sand spider	17 mm
Haplopelma	huwenum	Chinese bird spider			0.70 mg/kg http://www.spidertalk.net/SpiderTalk/post.php?action=reply&fid=1&tid=2165&repquote=16279		One infant death reported.
Poecilotheria	ornata	Fringed ornamental tarantula					Instances of coma reported.
Poecilotheria	fasciata **	Sri Lankan ornamental tarantula					Instances of cardiac failure reported
Tegenaria	agrestis	Hobo spider	7–14 mm				(1 reported)
Cheiracanthium	species	Yellow sac spider	6–10 mm				(No severe consequences)
Cheiracanthium	japonicum	Japanese sac	6–10 mm
Macrothele	holsti, gigas, taiwanensis	Primitive burrowing spiders					No deaths reported in Taiwan.http://www.disaster.org.tw/chinese/annmed/Vol3supp1/3.pdf
Steatoda	grossa	Cupboard spider					Mild widow-like symptoms reported, no severe consequences

* This value is based on experience with human exposures.
** Several other kinds of tarantulas in the pet trade are regarded as giving non-trivial bites. Tarantulas are typically far larger than spiders with the most toxic kinds of venom. However, the sheer volume of the venom may compensate for its lesser toxicity. The effects of a full envenomation are probably unknown for many species of tarantulas, so due caution is advisable.

Spiders and similar creatures with undeserved reputations

There are several species of spider (and a few other arachnids which are not spiders, but are frequently confused with them), who have had undeserved reputations for being harmful to humans. (In addition, it should be noted that some of the entries above, such as the hobo spider, are currently the subject of some debate in the scientific community).

Lycosa tarentula

Lycosa tarentula, a species of wolf spider which is found near Taranto, Italy (and the origin of the name tarantula, which today refers to a completely different kind of spider), was once blamed for a condition known as tarantism. Workers in the fields would suffer bites, and observe large, conspicuous, hairy spiders in the area. That spider, L. tarentula, was blamed for the pain and suffering (and occasional death) associated with tarantism. It is known that the bite of L. tarentula, while sometimes painful, has no serious medical consequences for humans. It is also suspected that the real culprit was another spider, Latrodectus tredecimguttatus, a type of widow spider, and one which is now known to be very dangerous to people.

White-tailed spider

The white-tailed spider, a species indigenous to Australia, has long been blamed for a necrotic bite, producing symptoms similar to a brown recluse. However, recent studies into this spider have led many to believe that its bite produces no serious effects in humans; in particular, necrotic ulcers were not observed. White-tail bites do cause localized pain and lesions. http://www.mja.com.au/public/issues/179_04_180803/isb10785_fm.html Ibister, Goeffrey K. and Gray, Michael R, "White-tail spider bite: a prospective study of 130 definite bites by Lampona species" Medical Journal of Australia 179 (4): 199-202 Nonetheless, the white-tailed spider still is rather infamous in Australia, and frequently referred to as a dangerous spider.

Harvestman (Daddy-long-legs)

The spider-like arachnids known as Opiliones (also known as harvestmen or daddy long-legs), are a species often handled by humans. They are the subject of an urban legend which claims that they possess venom which is deadly to humans, but have fangs which are unable to penetrate human skin, and thus are essentially harmless. In truth, these arachnids are completely harmless to humans, as they have no venom whatsoever. In addition, incidents of opiliones biting people are rare, and no reported bites by these species have had any lasting effects.

It should noted that the term "daddy long-legs" also can refer to the similar-looking cellar spider. This species (a true spider) can bite humans, but it's venom is not known to have any effects beyond mild discomfort at the site of the bite.

Sun spiders

The arachnids of the genus Solifugae, also known as wind scorpions or sun spiders, are neither spiders nor scorpions. In the Middle East, it is common belief among some American soldiers stationed there that Solifugae will feed on living human flesh. The story goes that the creature will inject some anaesthetizing venom into the exposed skin of its sleeping victim, then feed voraciously, leaving the victim to awaken with a gaping wound. Solifugae, however, do not produce such an anaesthetic, and, like most creatures with any sort of survival instinct, they do not attack prey larger than themselves unless threatened.

Further, solifugae are known to not possess any venom (other than one species in India, which may possess venom according to one study Aruchami, M. & G. Sundara Rajulu. 1978. "An investigation on the poison glands and the nature of the venom of Rhagodes nigrocinctus (Solifugae: Arachnida)". Nat. Acad. Sci. Letters (India), 1:191-192). However, due to the large size of their jaws, a bite by a solifugae can cause a significant wound, one which should be treated accordingly to avoid infection.

References

External links

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