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Which spider species is this, and is it dangerous?

Which spider species is this, and is it dangerous?


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Sorry for a quite bad picture. I was afraid to get closer!

Seen in Croatia, inlands, not near sea. As he is on the picture there with the legs stretched out, I'd say he was about 8-10 cm in length.


It is a female, the males of this genus are quite distinct. The genus is Argiope, and the specific epithet most probable is bruennichi. It is not a clinically important spider.


5 most dangerous spiders

Here we take a look at the fiven most dangerous spiders on earth.

Number 5: Red-back spider (Latrodectus hasselti)

The redback spider (Latrodectus hasseltii) is a dangerous spider endemic to Australia. It is a close cousin of pretty known black widow, which is found throughout the world. The female is easily recognisable by her black body with a prominent red stripe on the back of her abdomen. Females have a body length of about a centimetre, while the male is smaller, being only 3 to 4 mm long. The redback spider is one of few arachnids which usually display sexual cannibalism while mating.

Redbacks are considered one of the most dangerous species of spiders in Australia. Its neurotoxic venom is toxic to humans, with bites causing severe pain, often for over 24 hours. An antivenom is commercially available, and since its introduction in 1956, no deaths due to redback bites have been reported.+

Redback spider bites rarely cause significant morbidity, and deaths are even more rare. Throughout Australian history, only 14 deaths from redbacks have been recorded. Hundreds or even thousands of people are thought to be bitten each year across Australia, although only about 20% of bite victims require treatment. Children, the elderly, or those with serious medical conditions are at much higher risk of severe side effects and death resulting from a bite. The larger female spider is responsible for almost all cases of redback spider bites in humans.

Most bites occur in the warmer months between December and April, in the afternoon or evening. As the female redback is slow-moving, and rarely leaves its web, bites generally occur as a result of a person placing a hand or other body part too close to the web, such as when reaching into dark holes or wall cavities. Bites can also occur if a spider has hidden in clothes or shoes.

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Number 4: Sydney funnel-web spider (Atrax robustus)

The Sydney funnel-web spider (Atrax robustus) is a species of Australian funnel-web spider usually found within a 100 km (62 mi) radius of Sydney, New South Wales, Australia. It is a venomous spider with a bite capable of causing serious injury or death in humans if left untreated.

Funnel-web spider venom contains a compound known as atracotoxin, an ion channel inhibitor, which makes the venom highly toxic for humans and primates. However, it does not affect the nervous system of other mammals. These spiders typically deliver a full envenomation when they bite, often striking repeatedly, due to their defensiveness and large chitinous cheliceral fangs. There has been no reported case of severe envenoming by female funnel-web spiders, which is consistent with the finding that the venom of female specimen is less potent than the venom of their male counterparts. In the case of severe envenoming, the time to onset of symptoms is less than one hour with a study about funnel-web spider bites finding a median time of 28 minutes. There is at least one recorded case of a small child dying within 15 minutes of a bite from a Sydney funnel-web spider.

Since the antivenom became available in 1981, there have been no recorded fatalities from Sydney funnel-web spider bites. In September 2012, it was reported that stocks of antivenom were running low, and members of the public were asked to catch the spiders so that they could be milked for their venom. One dose of antivenom requires around 70 milkings from a spider.

When threatened or provoked, funnel-web spiders will display aggressive behaviour, rearing up on its behind legs and displaying their fangs. When biting, the funnel-web spiders maintain a tight grip on their victim, often biting repeatedly.

Number 3: Brazilian wandering spider (Phoneutria fera)

Brazilian wandering spiders, armed spider or banana spiders, are a genus of defensive and venomous spiders of potential medical significance to humans. They are mainly found in tropical South America, with one species in Central America.

The Brazilian wandering spiders appear in Guinness World Records from 2010 as the world’s most venomous spider. However, several venomous species of arachnid are far more likely to attack a human, and the Guinness book of World Records states that although the Brazilian wandering spider is the most toxic, more deaths actually occur from black widow and brown recluse spider bites, due to the rarity of the Wandering spider biting anyone.

Wandering spiders are so-called because they wander the jungle floor at night, rather than residing in a lair or maintaining a web. During the day they hide inside termite mounds, under fallen logs and rocks, and in banana plants and bromeliads. P. nigriventer is known to hide in dark and moist places in or near human dwellings.

Brazilian wandering spiders are widely considered the most venomous species of spider. At deadly concentrations, their venom causes loss of muscle control and breathing problems, resulting in paralysis and eventual asphyxiation. In addition, the venom causes intense pain and inflammation following a bite. Aside from causing intense pain, the venom of the spider can also cause erection which can last for many hours and can lead to impotence.

The spider’s wandering nature is another reason it is considered so dangerous. In densely populated areas, it usually search for cover and dark places to hide during daytime, leading it to hide within houses, clothes, cars, boots, boxes and log piles, thus generating accidents when people disturb it. Its other common name, “banana spider”, comes from its tendency to hide in banana bunches or plantations, and it is occasionally found as a stowaway within shipments of bananas. These spiders can also appear in banana crates sent to grocery stores and bulk food centers around the world.

Number 2: Brown recluse spider (Loxosceles reclusa)

Brown recluse spiders are usually between 6–20 mm ( 1 ⁄4 in and 3 ⁄4 in), but may grow larger. While typically light to medium brown, they range in color from cream-colored to dark brown or blackish gray. Most spiders have eight eyes recluse spiders have six eyes arranged in pairs (dyads) with one median pair and two lateral pairs. Only a few other spiders have three pairs of eyes arranged in this way. It is native to the United States from the southern Midwest south to the Gulf of Mexico.

The brown recluse spider is rarely aggressive, and bites from the species are uncommon. In 2001, more than 2,000 brown recluse spiders were removed from a heavily infested home in Kansas, yet the four residents who had lived there for years were never harmed by the spiders, despite many encounters with them. The spider usually bites only when pressed against the skin, such as when tangled within clothes, towels, bedding, inside work gloves, etc. Many human victims report having been bitten after putting on clothes that had not been worn recently, or had been left for many days undisturbed on the floor. However, the fangs of the brown recluse are so tiny they are unable to penetrate most fabric.

The bite frequently is not felt initially and may not be immediately painful, but it can be serious. The brown recluse bears a potentially deadly hemotoxic venom. The venom spreads throughout the body in minutes. The systemic symptoms most commonly experienced include nausea, vomiting, fever, rashes, and muscle and joint pain. Rarely, such bites can result in hemolysis,thrombocytopenia, disseminated intravascular coagulation, organ damage, and even death. Sometimes the bite forms a necrotizing ulcer that destroys soft tissue and may take months to heal, leaving deep scars. These bites usually become painful and itchy within 2 to 8 hours. Pain and other local effects worsen 12 to 36 hours after the bite, and the necrosis develops over the next few days. Over time, the wound may grow to as large as 25 cm (10 inches). The damaged tissue becomes gangrenous and eventually sloughs away.

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Number 1: Black Widow (Latrodectus mactans)

Latrodectus mactans, or Southern black widow or simply black widow, is a highly venomous species of spider. They are well known for the distinctive black and red coloring of the female of the species and for the fact that she will occasionally eat her mate after reproduction (hence the name – Black widow). The species is native to North America. The venom might be fatal to humans.

Although these spiders are not especially large, their venom is extremely potent. They are capable to inject the venom to a point where it can be harmful. The males, being much smaller, inject far less venom. The actual amount injected, even by a mature female, is very small in physical volume. 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 (though it can produce the very unpleasant symptoms of latrodectism). Sixty-three deaths were reported in the United States between 1950 and 1959. 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 to bites of more dangerous spiders, so the highest number of deaths worldwide are caused by members of this genus. Widow spiders have more potent venom than most spiders, and prior to the development of antivenom, 5% of reported bites resulted in fatalities. The venom can cause a swelling up to 15 cm. Improvements in plumbing have greatly reduced the incidence of bites and fatalities in areas where outdoor privies have been replaced by flush toilets.


Happy face spider

The Hawaiin happy face spider is only found in the rainforests of Hawaii. However, no one is quite sure why they have a smiling face on their back.

Some scientists believe that it’s to help confuse predators while others think that it helps them to blend into their surroundings by making it look as though they are merely rusted spots.

That’s not all. One study showed they change from yellow to green or orange depending on what they eat throughout the day. As if that wasn’t enough, they don’t use webs to capture their food, but they hunt it down and attack instead. Not so happy now.


Myth: Tarantulas are dangerous to humans

Fact: Outside of southern Europe (where the name is used for a wolf spider, famous in medieval superstition as the alleged cause of "tarantella" dancing), the word tarantula is most often used for the very large, furry spiders of the family Theraphosidae.

Hollywood is squarely to blame for these spiders' toxic-to-humans reputation. Tarantulas are large, photogenic and many are easily handled, and therefore they have been very widely used in horror and action-adventure movies. When some "venomous" creature is needed to menace James Bond or Indiana Jones, to invade a small town in enormous numbers, or to grow to gigantic size and prowl the Arizona desert for human prey, the special-effects team calls out the tarantulas!

In reality, the venom of these largest-of-all-spiders generally has very low toxicity to humans. I myself was once bitten by a Texan species and hardly even felt it. None of the North American species or those commonly kept as pets are considered to pose even a mild bite hazard. There have now been a few credible reports of moderate illness from the bites of a few African and Asian species that are definitely not standard pet store material. However, other people bitten by these same species reported no more than an initial "ouch" and perhaps a little muscle cramping.

The only health hazard posed by keeping common pet tarantulas comes from the irritating hairs of the abdomen (in New World species), which can cause skin rashes or inflammation of eyes and nasal passages. To prevent such problems, simply keep tarantulas away from your face and wash your hands after handling one.

Compared to common pets such as dogs, tarantulas are not dangerous at all. (For more information, see the American Tarantula Society).

Not dangerous to humans

Both the European wolf spiders originally called tarantulas, and the theraphosid spiders, often kept as pets and called tarantulas now, have been reputed dangerous to humans. They aren't.

"Everything that 'everybody knows' about spiders is wrong!" —Rod Crawford sets the record straight with Spider Myths.


Brown Recluse Spider

Brown recluse spiders tend to be thinner and less hairy than wolf spiders and their bite is more serious

One of the most dangerous arachnids to find in your home is the brown recluse spider (scientific name: Loxosceles reclusa) from the family Sicariidae. Like with other species of recluse spiders, a bite from one of these brown arachnids can require medical attention.

Spider Facts

Excluding their 8 legs, brown recluse spiders range in size from 0.24” to 0.79” (6 – 20 mm). Due to their violin-shaped markings on their rear, they are also called ‘violin spiders,’ ‘fiddleback spiders,’ or ‘brown fiddlers.’ Their long spindly legs make them look bigger than they actually are.

Unlike most other spiders, brown recluses have 3 pairs of eyes rather than 4. They usually scurry away when they feel threatened but if cornered, they may bite. This can result in serious skin tissue injury if not treated properly.

Identifying features

These spiders can be tiny in size or grow to be large spiders nearly an inch (2.5 cm) long. They are usually light tan to medium brown and some species can be dark brown or gray.

These spiders prefer isolated locations and create webs in garages, woodpiles, sheds, and cellars. They are found in many states in central and eastern U.S. such as Texas, Nebraska, Ohio, Georgia, and Kentucky.


Arachnophobia may be embedded in your DNA

Arachnophobia, the fear of spiders, is one of the most common phobias humans have. But out of all the spiders that live today, really very few are dangerous – so why is it that we fear them so much then? Researchers from Columbia University believe they might have found the answer to that – and it’s strictly related to human evolution.

Tens or hundreds of thousands of years ago, early humans were starting to emerge in east Africa – what we call today the cradle of mankind. Back then and in that area, most spiders they would have encountered posed a great threat to humans, because they were poisonous. During our species’ early evolutionary phases, running into a spider could have been extremely dangerous – so fearing it and being able to avoid it would have been a direct evolutionary advantage.

Joshua New, assistant professor at Columbia University believes that early humans became so afraid of spiders that even after all these years, the phobia is still embedded in our DNA.

“A number of spider species with potent, vertebrate-specific venoms populated Africa long before hominoids, and have co-existed there for tens of millions of years. Humans were at perennial, unpredictable and significant risk of encountering highly venomous spiders in their ancestral environments. Even when not fatal, a black widow spider bite in the ancestral world could leave one incapacitated for days or even weeks, terribly exposed to dangers.”

In order to test out their theory, researchers had 252 volunteers were study computer screens containing abstract shapes and data. Their reactions to images of spiders were especially fast, even if their shape was distorted. An distorted image of a spider produced a much stronger reaction than a clear image of a fly or a needle, for example.

“This ability (to pick out spiders more quickly) was highly specific to stimuli which conformed to a spider ‘template’: participants were frequently inattentionally blind to scrambled versions of the spider stimuli, and to a modern threat (hypodermic needle), and even a different animal (housefly). This demonstrates that some evolutionary-relevant threats are highly-specified and can evoke what is perhaps best termed ‘reflexive awareness’: an immediate and elaborated perception sufficient to guide an adaptive behavioral response.”

These findings fall in line with a previous study at the Emory University School of Medicine that found that fear can be passed on through genes. But the idea that the fear of spiders is passed through genetically isn’t the only theory out there – some scientists claim that learned experience play a much bigger role. Jon May, a professor of psychology at Plymouth University, believes that fearing spiders is a learned condition: when parents or friends react in a specific way (they are afraid of spiders), or even when this is portrayed in the media, children pick this up. Spiders also have specific features (unpredictable movements, angular legs and dark colours) which accentuate the fear. According to Professor May:

“Spiders just tick all these boxes, and like any phobia, when it builds up in someone’s mind they can become scared even seeing a picture. We like bright-coloured butterflies and ladybirds, but spiders are dark coloured with long angular legs – and the shape and colour both have strong negative associations. We are also very sensitive to seeing things moving out of the corner of our eye and immediately notice it, and insects move quickly and unpredictably.”


THE MOST DANGEROUS SPIDERS In The World(video)

But before we head into the list, let’s shed some more light on the topic before we head onto the list.

Should You Be Afraid of Venomous Spiders? Are All Spiders Dangerous?

We know that most people, especially those with Arachnophobia (the fear of spiders) would be completely freaking out right now. But let’s not jump to conclusions here.

Yes, it’s true that all spiders contain venom. This venom contains neurotoxins that are used by spiders to immobilize their prey long enough to catch them. Luckily, the venom of the majority of spiders is too weak to cause any damage to humans. To give you a rough example, out of more than 3,000 species of spiders in the United States, only 2 are capable of doing any actual damage to humans with their venom.

More than that, spiders don’t particularly consider humans as their prey. In fact, most spiders will try to hide or run away or sometimes even play dead if they encounter a human. They will only consider biting humans as a last resort and will do so in defense.

In addition to this, you should also know that spiders only have a limited amount of venom in their bodies. Even if one of the most dangerous spiders in the world bites you, they’ll only release enough venom to allow them to escape unharmed. This quantity, even from some of the most dangerous spiders, would be highly unlikely to cause death.

You can also take comfort from the fact that antivenin is now available for almost all of the dangerous species of spiders around the world. So, if you suspect that a dangerous spider has bitten you, you can visit a hospital where you’ll be administered with an antivenin. Since the development of antivenins, deaths from the bite of even the most dangerous spider in the world (Sydney Funnel-Web Spider) has come down to zero.


5. Brown Widow Spider, Grey Widow Spider

The brown or grey widow spider (Latrodectus geometricus) carries a similar neurotoxin as the black widow (see below) but delivers less toxin. While painful, their bites typically affect only the immediate area and are therefore less dangerous to humans.

Brown widow spiders are smaller and paler than black widows. Like others in the species, they have an hourglass-shaped marking on their abdomen. However, the markings in these species are a vivid orange or yellow. Unlike its relatives, the brown widow spider has a black and white geometric pattern on its abdomen’s dorsal side.

Brown widow spiders are found all over the continental US, as well as Hawaii. There have been recent indications of this species overtaking black widow spiders in certain locales, including Southern California, which is good news for humans since they pose less danger.


4. Redback / Black Widow Spider (Latrodectus)

The black widow spider, or redback as it is known in Australia is one of the most iconic spiders on the planet. Instantly recognisable by its round black abdomen with striking red markings these are definitely spiders not to be trifled with. Both the redback and the black widow are from the Latrodectus family with the redback being marginally more venomous than the black widow. And that venom is potent, more so than any other spider but one. The only reason these spiders don’t top the list is because they are smaller and deliver less of it.

The effects of this lethal toxin range from burning pain to a systemic condition known as latrodectism. Symptoms include general pain and swelling spreading from the affected area, abdominal cramps, nausea and sweating to name a few. This condition occurs in around half of bites and was often fatal in the very old and young before anti venom became available.


Which spider species is this, and is it dangerous? - Biology

The brown recluse spider, Loxosceles reclusa Gertsch & Mulaik, is frequently reported in Florida as a cause of necrotic lesions in humans. For example, in the year 2000 alone, Loft (2001) reported that the Florida Poison Control Network had recorded nearly 300 alleged cases of brown recluse bites in the state a subset of 95 of these bites was reported in the 21 counties (essentially central Florida) under the jurisdiction of the regional poison control center in Tampa.

Figure 1. Female brown recluse spider, Loxosceles reclusa Gertsch & Mulaik. Photograph by Jeffrey Lotz, DPI.

I called the Florida Poison Control Network to confirm these numbers, and was cited 182 total cases and 96 in the Tampa region. The actual numbers are less important than the fact that a significant number of unconfirmed brown recluse spider bites are reported in the state every year. Yet not one specimen of brown recluse spider has ever been collected in Tampa, and the only records of Loxosceles species in the entire region are from Orlando and vicinity. A general review of the brown recluse, along with a critical examination of the known distribution of brown recluse and related spiders in Florida, seems in order at this time.

Distribution (Back to Top)

Loxosceles reclusa was described by Gertsch and Mulaik (1940) from Texas. At the time of the first revision of the genus Loxosceles in the Americas (Gertsch 1958), the known distribution ranged from Central Texas to southern Kansas, east through middle Missouri to western Tennessee and northern Alabama, and south to southern Mississippi. Gorham (1968) added Illinois, Kentucky and northern Georgia. Later, he added Nebraska, Iowa, Indiana and Ohio, with scattered introductions in other states, including Florida his map indicated a record in the vicinity of Tallahassee (Gorham 1970).

Weems and Whitcomb (1975) noted that, "on many occasions specimens have been inadvertently brought into Florida in trucks and automobiles, hidden in luggage, boxes, and various commercial cargoes, but to date it appears to have been unsuccessful in establishing breeding populations in Florida." It is unfortunate that they did not document these alleged records, as this comment is not completely in accord with the following reference.

An updated revision of the genus by Gertsch and Ennik (1983) reported a few records from Arizona, California, Colorado, Florida, Maine, Minnesota, New Jersey, New Mexico, New York, North Carolina, Wyoming and Tamaulipas (Mexico) [the reported Ontario (Canada) record in this publication subsequently proved to be a specimen of Loxosceles rufescens (Dufour) R. Vetter, personal communication, 2001]. Most of these peripheral records were interceptions of one or two specimens, not evidence of established populations. The Florida records consisted of two specimens, one each from Alachua (collected 10 January 1969) and Jefferson (Monticello, collected 21 August 1968) counties, and both were taken from inside automobiles. Subsequently, a sailor was bitten on the hand by a male brown recluse in the cargo hold of a naval ship in Jacksonville, in March 1986. This ship had just arrived from North Carolina, where it had loaded supplies. To date, this appears to be the only verified case (the actual causative agent of a bite captured and identified) of brown recluse spider bite in Florida [due to complicating factors, medical personnel familiar with this case even questioned the veracity of this one alleged bite].

Within the last two years, single buildings (in Callaway, Jacksonville and Tallahassee) have been found to contain populations of Loxosceles reclusa (Edwards 1999, 2000, 2001). There is reason to believe that all three of these records are the result of movement of infested materials from other states, so it is entirely possible that the infestations are restricted to these buildings and can be eliminated. Such was the case with an infestation of the similar Loxosceles rufescens found in Orange County (DPI records from Orlando: 28 January 1982, 4 January 1983 and 18 August 1986) in a single building the spiders were subsequently eradicated.

The only other records of Loxosceles rufescens occurring in Florida are a few juvenile spiders in buildings in nearby Osceola County (Runnymede Banks 1904) and one juvenile specimen from Dade County (Lemon City Gertsch 1958). This cosmopolitan species is probably native to the Mediterranean region, and is sometimes called the Mediterranean brown spider or Mediterranean recluse. It has been recorded from a number of localities across the U.S., particularly in larger cities, where it is transported by commerce (Gertsch and Ennik 1983).

In summary, the verified records of brown recluse and related spiders in the state are limited to the following eight out of 67 Florida counties: Alachua, Bay (Callaway), Dade (Lemon City), Duval (Jacksonville), Jefferson (Monticello), Leon (Tallahassee), Orange (Orlando) and Osceola (Runnymede). The more northern counties (Alachua, Bay, Duval, Jefferson and Leon) were all isolated records of the native brown recluse, Loxosceles reclusa, whereas the more southern county records (Dade, Orange and Osceola) were of the introduced Mediterranean recluse, Loxosceles rufescens. The Alachua, Dade and Jefferson county records were interceptions of single specimens. The Bay, Duval, Leon, Orange and Osceola county records were infestations in one or two buildings. There is no evidence to support either the notion that a widespread population of brown recluse spiders exists in Florida or that there are numerous introductions of brown recluse into the state. Therefore, there is no reason to assume that frequent interactions between brown recluse and humans occur in Florida. Subsequent to the original publication of this work (as a DPI Entomology Circular), Loxosceles rufescens was found in a warehouse in Escambia County, Florida and Loxosceles laeta (Nicolet), the Chilean recluse spider, was found in a home in Polk County, Florida (Edwards 2002a).

I have personally identified several hundred Florida spiders submitted for identification by the public, and only one specimen (the Bay County record) proved to be a brown recluse spider. In addition, I have seen thousands of Florida spiders submitted by professional biologists and inspectors, with only the few specimens mentioned above proving to be members of the genus Loxosceles. It appears obvious to me that the chance of interaction between brown recluse spiders and people in Florida is close to nil, agreeing with Vetter's (2000) assessment of reported brown recluse bites outside the natural range of the spider. Medical personnel should, therefore, consider a multitude of more likely causes (see below) before diagnosing and treating a necrotic wound as a brown recluse bite.

Description (Back to Top)

The description is taken from Gertsch (1958). Adults of both sexes are similar in appearance and size, ranging from about 7 to 12 mm in body length. Adult females average slightly larger, about 9 mm compared to about 8 mm for adult males. The carapace is pale yellow to reddish brown, with a dusky brown patch just in front of the median groove (which is encompassed by a narrow, dark line) this patch is united to the front of the carapace by dusky brown stripes. In total, these markings appear in the form of a violin. In addition, three dusky patches may occur along the margin on each side. The sternum is yellowish, with other ventral body parts of the cephalothorax darker reddish brown.

Figure 2. Detail of the carapace of the brown recluse spider, Loxosceles reclusa Gertsch and Mulaik, showing the dark fiddle-shaped marking often used to identify this spider. Photograph by James L. Castner, University of Florida.

The legs are slender and dusky orange to dark reddish brown. They are numbered front to back with Roman numerals (I, II, III, IV). In females, the leg length formula, longest to shortest, is II, IV, I, III, typically with leg II being over 18 mm in length, and leg III about 15 mm, the other two pair intermediate in length. The male leg formula is II, I, IV, III, with leg II over 24 mm and leg III about 17 mm. The abdomen of both sexes is tan to brown, but it may appear darker if the spider has recently fed. Juveniles are paler in all respects, as are occasional adults.

Figure 3. Adult brown recluse spider, Loxosceles reclusa Gertsch and Mulaik, showing leg length relative to a US quarter. Photograph by Jim Kalisch, University of Nebraska-Lincoln.

Males of the common southern house spider, Kukulcania (= Filistata) hibernalis (Hentz), are frequently confused with the brown recluse (Edwards 1983). The male palp length of Loxosceles reclusa is under 4 mm, considerably less than the superficially similar crevice spider. Another difference between the two species is that Loxosceles reclusa has six eyes composed of three isolated pairs (dyads), whereas Kukulcania hibernalis has eight eyes all clumped together in the middle front of the carapace.

Figure 4. Male southern house spider, Kukulcania hibernalis (Hentz). Photograph by Jeffrey Lotz, Division of Plant Industry.

Figure 5. The three pairs of eyes that help identify the brown recluse spider, Loxosceles reclusa Gertsch and Mulaik. Photograph by Jim Kalisch, University of Nebraska-Lincoln.

The only other Florida spiders with an eye arrangement similar to Loxosceles are the spitting spiders of the genus Scytodes, but these spiders have a domed carapace, lack a violin-shaped carapace marking, and are not known to cause serious wounds in humans. Occasionally, the huntsman spider, Heteropoda venatoria (Linnaeus), is misidentified as a brown recluse (Edwards 1979). However, the color pattern on the carapace of this species is reversed, with a light median mark on a dark background, and adults of this spider are much larger than a brown recluse.

Figure 6. Female spitting spider, Scytodes sp. Photograph by G.B. Edwards, DPI.

Figure 7. Adult male huntsman spider, Heteropoda venatoria (Linnaeus). Photograph by Marie Knight.

Biology (Back to Top)

Hite et al. (1966) made the earliest thorough report of the biology of Loxosceles reclusa. In their study, they recorded the habitat of 626 brown recluse in Arkansas found from May 1962 to December 1964. Most (430) were found in buildings and outbuildings, especially in boxes and among papers, in every room from basement to attic. They were found in almost any place which had remained undisturbed for lengthy periods of time, such as behind pictures, beneath or behind furniture, in boxes of toys, in clothing, among stored papers, in the corrugations of cardboard boxes, and in discarded articles, such as tires, inner tubes, and assorted other junk. Most of the specimens found in feral conditions were under rocks, especially in bluff outcrops, with a few under bark or in logs. They definitely seemed to prefer dry conditions.

Spiderlings appear to stay with their mother for three to four instars before dispersing. They feed on prey provided by the mother during this time. Once dispersed, they may establish a home territory, where they stay through several more instars, as evidenced by the presence of several successive molts. Spiders go through a total of eight instars. Irregular webbing is seen in the nest area. Prey consists of a variety of other arthropods, including rather dangerous prey like other spiders and ants. The attack consists of a sudden lunge and bite, usually on an intended prey's appendage, after which the brown recluse immediately backs away (personal observation). The venom acts rapidly to paralyze the prey, preventing any retaliation for the initial attack of the recluse spider. After the prey is overcome by the venom, the brown recluse moves in to feed. Relatively harmless prey, particularly mobile prey like houseflies, will be held with the initial bite and not released.

Most mating and reproduction occurs during June and July. Females were frequently found with more than one eggsac. In the laboratory, females made up to five eggsacs. Total eggs per female ranged from 31 to 300, total hatched young maximized at 158 for a single female the largest number of young from one eggsac was 91 and percent emergence of young was 0 to 100. Some eggs were fed on by spiderlings from previous eggsacs still in the web, or even by the female (perhaps these were infertile). The egg stage averaged about 13 days, instars I-VIII 17, 110, 63, 41, 38, 34, 40, and 53 days respectively. Maximum age for a brown recluse from emergence to death was 894 days for a female, 796 for a male. A laboratory-kept specimen lived over six months without food or water. Captive specimens also proved moderately resistant to pesticides. These two characteristics illustrate why brown recluse populations may exist in buildings for long periods of time, despite repeated efforts to eradicate them.

Figure 8. Female brown recluse spider, Loxosceles reclusa Gertsch & Mulaik, with eggsac. Photograph by Jeffrey Lotz, DPI.

Bites and Bite Symptoms (Back to Top)

Brown recluse spiders usually bite only when they become trapped next to the victim's skin. Bites occur either when sleeping humans roll onto the spider or put on clothes into which the spider has crawled (Vetter and Visscher 1998). Typically bites occur under clothing, mostly on the thigh, upper arm, or lateral torso, less often on the neck (Anderson 1998) [Dr. Philip C. Anderson is a physician and medical researcher who has worked on brown recluse bites and venom for 40 years].

Description of the symptoms is from Wingo (1960), Gorham (1968, 1970), Anderson (1982, 1998), and Vetter and Visscher (1998). Reactions to a bite vary from no noteworthy symptoms to severe necrosis or systemic effects. Discomfort may be felt immediately after the bite, or several hours may pass before any local reaction to the bite occurs. In one study, only 57% of the patients realized they had been bitten at the time of the bite. It must be realized that there are at least two significant variables affecting the outcome of a bite. The first is the amount of venom injected by the spider. Like some venomous snakes, spiders are known to sometimes give "dry" bites, with little or no venom injected. The second variable is the sensitivity of the victim. Some people are simply more prone to have a severe reaction in instances where another person might only have a slight reaction.

Typical symptoms are as follows: Symptoms start two to six hours after the bite. Blisters frequently appear at the bite site, accompanied by severe pain and pronounced swelling. A common expression is the formation of a reddish blister, surrounded by a bluish area, with a narrow whitish separation between the red and blue, giving a "bull's-eye" pattern. By 12 to 24 hours, it is usually apparent if a Loxosceles wound is going to become necrotic because it turns purple in color if necrotic symptoms do not express by 48 to 96 hours, then they will not develop. If the skin turns purple, it will then turn black as cells die. Eventually the necrotic core falls away, leaving a deep pit that gradually fills with scar tissue.

Experimental antivenin (Rees et al. 1981 not commercially available) was very successful when administered within 24 hours, but many times a victim does not seek treatment until after necrosis is well underway (more than 24 hours), after which the antivenin is less effective. Systemic effects usually take two to three days to show symptoms. Bites that become systemic usually do not also become necrotic it is thought that in necrotic wounds the venom is localized in the tissue whereas in systemic reactions the venom is distributed quickly into the body without necrotic local effects. The wound is usually free of bacterial infection for the first two to three days but may be contaminated by patients due to pruritis (itching) leading to scratching. Recluse venom can exhibit extended necrosis in adipose (fatty) tissue of thighs, buttocks and abdomen of obese patients there is also a gravitational flow of the venom effects, at times leading to satellite pockets of necrosis. Healing can take weeks to months and may leave an unsightly scar, although scarring is minimal in most cases. Skin grafts may be required to complete healing in the worst cases, but should be considered a last resort.

Medical Analysis (Back to Top)

The following technical analysis is condensed from the medical literature. Persons who suspect they have been victimized by a brown recluse spider bite are strongly encouraged to consult with a physician.

In medical terms (Vetter 1998), bites from Loxosceles can be unremarkable (requiring no care), localized (requiring some care but usually healing without intervention), dermonecrotic (a slow- healing, necrotic ulcerated lesion needing supportive care), or systemic (vascular and renal damage, sometimes life-threatening). Within 10 minutes of venom injection, there is a constriction of capillaries around the site of the bite. A major venom component is sphingomyelinase D which causes hemolysis (destruction of red blood cells). Recluse venom has a strong disruptive effect on endothelial tissue. Polymorphonucleocytes (PMN) are activated (by the patient.s immune system) and infiltrate the bite site in test animals where PMN activity was suppressed, degree of necrosis was lessened. General symptoms are edema (swelling), erythema (redness caused by blood being brought to the surface to counteract the damage), pruritis (itching), pain at the site, and mild fever. A pruritic or painful eruption can occur within a few hours of the bite and persist for a week, ending with scaling and peeling of the hands, and a truncal papular rash, that recalls pictures of scarlet fever rashes the pruritis may be worse for the patient than the painful focal necrosis. The skin may feel hot and tender to the patient. It may be advisable to treat the rash and pruritis symptoms with Prednisone (Anderson 1998). Treatment with corticosteroids does not appear to affect either the skin necrosis or the hemolysis (Anderson 1998).

Dermatologic expression varies. In mild self-healing wounds, the bite site may not progress past an edematous erythema these wounds do not become necrotic and non-intrusive care is sufficient. In more serious wounds, a sinking blue-gray macule on the skin contains a "bull's- eye" pattern formation where a central erythematous bleb (blister) is separated from a peripheral cyanotic region by a white zone of induration (red-white-blue). If the bite becomes violaceous within the first few hours, this usually indicates that severe necrosis may occur and more supportive measures are necessary.

The initial bleb gives way to ischemia (localized temporary blood deficiency). A central eschar (hardened scab similar to that made after burns) forms, hardens, and within seven to 14 days the eschar falls out leaving behind an ulcerated depression. The necrosis may continue to spread from the bite site possibly due to an autoimmune response (see above). Normally, the wound limits begin to recede after one week as healing begins. Unnecessary removal of tissue often leads to greater scarring than would result from normal healing. Extirpation of damaged skin is only recommended in severe cases and only after the limits of the wound are strongly demarcated at six to eight weeks. Most wounds self-heal with excellent results.

Systemic conditions that might manifest in severe cases are hematoglobinuria (hemoglobin in the urine), hematoglobinemia (reduction of useful hemoglobin, resulting in anemia-like condition), thrombocytopenia (reduction of clotting platelets in the blood), and/or disseminated intravascular coagulation (DIC) (precipitation of platelets causing mini-clots all over the body). The presence of sustained coagulopathy with hemolysis indicates severe systemic loxoscelism. Fortunately, less than 1% of cases exhibit these symptoms. Although rare, if death occurs, it is most often from hemolysis, renal failure and DIC children are most adversely affected due to their small body mass. Anderson (1998) noted, however, that none of the fatalities were proven to have been caused by a brown recluse spider.

Alternatives to Consider in Suspected Cases of Brown Recluse Bite

Spider bites cause clean infarctions in the skin. If an inflammatory core lesion exists, necrotizing infection should be anticipated, not spider bite. A number of other arthropods and an assortment of diseases, some caused by microorganisms and some with other causes, are known to produce necrotic or apparent pre-necrotic wounds. Vetter (1998) gives a list of causative agents of necrotic wounds (related discussion can be found at the associated website). This list includes most of the following conditions:

Tick-induced: tick bites and tick-borne diseases, such as erythema chronicum migrans (Lyme disease) and Rocky Mountain Spotted Fever

Viral: chronic herpes simplex, infected herpes simplex, herpes zoster (shingles)

Bacterial: Gonococcal (G.C.) arthritis dermatitis, Mycobacterium ulcerans, Staphylococcus infection, Streptococcus infection

Fungal: keratin cell mediated response to a fungus, sporotrichosis

Blood Disorders: focal vasiculitis, purpura fulminans, thromboembolic phenomena

Underlying Disease States: diabetic ulcer, chronic liver disease (spontaneous necrotizing fasciitis), pyoderma gangrenosum, toxic epidermal necrolysis (Lyells syndrome)

Cancer: leukemia, lymphomatoid papulosis (LyP), lymphoma

Reaction to Drugs/toxins: alcoholism, erythema nodosum, warfarin and heparin poisoning

Topical: chemical burn (e.g., oven cleaner), poison ivy/oak infection

Miscellaneous/ Multiple Causative: bed sores, erythema multiforme, Stevens-Johnson syndrome, self-inflicted wounds

Unknown Causative Agents: periarteritis nodosa.

Other possibilities include subcutaneous blisters and hives caused by stings of hymenopterous insects (ants, bees, yellowjackets, wasps), welts from urticating caterpillars, bites by predatory or parasitic bugs (assassin bugs, bed bugs), and other parasitic insect bites (black flies, mosquitoes, horse and deer flies, fleas). It is even possible that some as yet untested native spider is the cause of serious necrotic wounds. For example, circumstancial evidence in one case implicated Ctenus captiosus Gertsch (Edwards 1989), a wandering spider, as a cause of a necrotic bite, although a recent assay of the venom of this species did not find sphingomyelinase D (Dr. G. J. Bodner, personal communication, 2001).

The expression of Lyme disease can give the classic 'bull's-eye' patterning characteristic of brown recluse bite. Although Lyme disease is rare in Florida, it does exist and would be a more probable diagnosis than brown recluse bite. Misdiagnosis in this case could be serious since Lyme disease can be treated and cured with common antibiotics. If diagnosed as 'brown recluse bite' instead, it will obviously be treated as such the Lyme disease then may progress to serious symptoms of heart and central nervous system disorders, and can result in death. In treating alleged spider bite victims, a question that medical personnel should be asking is whether the patient has recently traveled outside the area where they live. They should also attempt to be aware of potentially embarrassing etiological agents such as filthy lifestyle habits (squalid conditions that might encourage vermin such as bed bugs) or unhygienic use of drug paraphernalia (Vetter 1998).

Postscript

Anderson (1982) made perhaps the most appropriate comment concerning spider bites, "In general, spiders attempt to avoid people. People should accommodate them."

Acknowledgments

Dr. D. Sollee, Florida Poison Control Network, provided statistics on brown recluse bites in Florida. R. Vetter, University of California, Riverside, reviewed the manuscript and contributed valuable discussions about brown recluse distribution and bites.

Selected References (Back to Top)

  • Anderson PC. 1982. Necrotizing spider bites. American Family Practitioner 26: 198-203.
  • Anderson PC. 1998. Missouri brown recluse spider: a review and update. Missouri Medicine 95: 318-322.
  • Banks N. 1904. The Arachnida of Florida. Proceedings, Academy of Natural Science, Philadelphia 56: 120-147.
  • Dominquez TJ. 2004. It's not a spider bite, it's community-acquired methicillin-resistant Staphylococcus aureus. Journal of the American Board of Family Practice 17: 220-226.
  • Edwards GB. 1979. The giant crab spider, Heteropoda venatoria (Linnaeus) (Araneae: Sparassidae). Florida Department of Agriculture and Consumer Services (FDACS), Division of Plant Industry, Entomology Circular 205 1-2.
  • Edwards GB. 1983. The southern house spider, Filistata hibernalis Hentz (Araneae: Filistatidae). FDACS, Division of Plant Industry, Entomology Circular 255: 1-2.
  • Edwards GB. 1989. The Florida false wolf spider, Ctenus captiosus (Araneae: Ctenidae). FDACS, Division of Plant Industry, Entomology Circular 319: 1-2.
  • Edwards GB. 1999. Insects of Medical and Veterinary Importance, In Halbert SE. (editor). FDACS, Division of Plant Industry, Tri-Ology (Entomology Section) 38: 8.
  • Edwards GB. 2000. Insects of Medical and Veterinary Importance, in Halbert, S.E., ed., FDACS, Division of Plant Industry, Tri-Ology (Entomology Section) 39: 8.
  • Edwards GB. 2001. Insects of Medical and Veterinary Importance, in Halbert, S.E., ed., FDACS, Division of Plant Industry, Tri-Ology (Entomology Section) 40: 8.
  • Edwards GB. (2002a). Chilean recluse, Loxosceles laeta (Nicolet) (Araneae: Sicariidae) in Florida. Pest Alert. (no longer available online).
  • Edwards GB. (2002b). Venomous Spiders in Florida. Pest Alert. (no longer available online).
  • Gertsch WJ. 1958. The spider genus Loxosceles in North America, Central America, and the West Indies. American Museum Novitates 1907: 1-46.
  • Gertsch WJ, Ennik F. 1983. The spider genus Loxosceles in North America, Central America, and the West Indies (Araneae, Loxoscelidae). Bulletin, American Museum of Natural History 175: 265-360.
  • Gertsch WJ, Mulaik S. 1940. The spiders of Texas. I. Bulletin, American Museum of Natural History 77: 307-340.
  • Gorham JR. 1968. The brown recluse spider Loxosceles reclusa and necrotic spiderbite - A new public health problem in the United States. Journal of Environmental Health 31, 8 pp.
  • Gorham JR. 1970. The brown recluse. United States Department of Health, Education, and Welfare, Public Health Service Publication 2062.
  • Hite JM., Gladney WJ, Lancaster JL Jr., Whitcomb WH. 1966. Biology of the brown recluse spider. University of Arkansas, Agricultural Experiment Station Bulletin 711: 1-26.
  • Loft K. 2001. DO NOT DISTURB. BayLife, Tampa Tribune, May 22, 2001.
  • Rees R, Shack RB, Withers E, et al. 1981. Management of brown recluse spider bite. Plastic Reconstructive Surgery 68: 768-773.
  • Vetter RS. (2003). Causes of necrotic wounds other than brown recluse spider bites. University of California, Riverside, Entomology Insect Information, Spiders and other Arachnids. (9 October 2018).
  • Vetter RS. 2000. Myth: idiopathic wounds are often due to brown recluse or other spider bites throughout the United States. Western Journal of Medicine 173: 357-358.
  • Vetter RS, Edwards GB, James LF. 2004. Reports of envenomation by brown recluse spiders (Araneae: Sicariidae) outnumber verifications of Loxosceles spiders in Florida. Journal of Medical Entomology 41: 593-597.
  • Vetter RS, Visscher PK. 1998. Bites and stings of medically important venomous arthropods. International Journal of Dermatology 37: 481-496.
  • Weems HV Jr., Whitcomb WH. 1975. The brown recluse spider, Loxosceles reclusa Gertsch and Mulaik (Araneae: Loxoscelidae). FDACS, Division of Plant Industry, Entomology Circular 158: 1-2.
  • Wingo CW. 1960. Poisonous spiders. University of Missouri, Agricultural Experiment Station Bulletin 738: 1-11.

Authors: G.B. Edwards, Florida Department of Agriculture and Consumer Services, Division of Plant Industry.
Originally published as DPI Entomology Circular 406.
Photographs: Jeffrey Lotz and G.B. Edwards, Division of Plant Industry Jim Kalisch, University of Nebraska - Lincoln and James L. Castner, University of Florida
Web Design: Don Wasik, Jane Medley
Publication Number: EENY-299
Publication Date: August 2003. Latest revision: August 2015. Reviewed October 2018.

An Equal Opportunity Institution
Featured Creatures Editor and Coordinator: Dr. Elena Rhodes, University of Florida



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