Is this a venomous (poisonous) spider?

Is this a venomous (poisonous) spider?

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Today I found a spider in my home that I have never seen before. I live in Karachi, Pakistan.

I want to know which spider is this and if it is venomous and danger for me or my family ?? Is this spider commonly found in homes. I have seen many home spiders but they were never like that.

The spider is around 2cm long (front legs to back legs span as shown in 1st image)

This looks like either a young or rather hungry Theridiid spider. I am not particularly experienced with Eurasian spiders, but as far as I know, the only Widows you're likely to come across in Karachi are either the Redback (Latrodectus hasselti) or the relatively non-problematic Brown Widow (Latrodectus geometricus). This does not appear to be either of these - the front pair of legs is nice and long, but the abdomen is too plain and the bands at the leg joints are not particularly dark brown and contrasting.

Young female Brown Widow from Bug Guide:

Male Widows, both Black and Brown, tend to have small, rather stripy abdomens, and as adults, will have enlarged ball-like structures at the end of the face-mounted pedipalps.

Male Black Widow from Bug Guide:

That just leaves one of the medically unimportant Theridiids as the most likely candidate, and that's where I unfortunately cannot help any further. Still, the rule of thumb is that unless you identify it as a problem biter, it's not worth worrying about. The trick is to look at its underside. If it shows a red hourglass, it's a problem - if not, no worries. Judging by the photos, I'd go with "no worries", unless you can come up with a clear image of something troublesome.

I include references to support my claims regarding the distribution of Widows in Pakistan:

A venom is a secretion that an animal produces in a gland for the purpose of injecting it into another animal. It is actively introduced into a victim by means of a specialized apparatus. Venomous organisms use a wide variety of tools to inject venom: barbs, beaks, fangs or modified teeth, harpoons, nematocysts (found in jellyfish tentacles), pincers, proboscises, spines, sprays, spurs, and stingers.

Animal venoms are generally a mix of proteins and peptides, and their precise chemical makeup to a large extent depends on the purpose of the venom. Venoms are used for defense against other creatures or for hunting prey. Those used for defense are designed to create immediate, localized pain to make another animal go away. The chemistry of venoms designed for hunting prey, on the other hand, is highly variable, since these venoms are made specifically to kill, incapacitate, or break down the victim's chemistry to make it easily edible. If cornered, many hunters will use their venom for defense.

Pick your poison

Poisonous species only deploy their toxins defensively, to avoid being eaten by predators, says David Nelsen, a biologist at Southern Adventist University in Tennessee. This is why venoms bypass the digestive system via wounds to the body.

When ingested by a predator, for example, these toxins travel through the body quickly, causing temporary illness or death, depending on the poison and the dose. Pufferfishes, for instance, are especially deadly due to a neurotoxin in their skin and organs that's more toxic than cyanide.

Many poisonous animals don’t manufacture their own defenses, instead gleaning them from sources in their environment. Pufferfishes, for example, get their tetrodotoxin from a marine bacterium. As caterpillars, monarch butterflies eat toxic milkweed plants, which gives them a bitter taste in adulthood.

Don't fear the pholcid: Daddy long-legs' venom is only dangerous if you're an insect

Credit CC2.5, Akio Tanikawa

You've probably heard the urban legend: Daddy long-leg spiders possess extremely toxic venom—so toxic that it would kill a human if only their fangs were long/strong enough to penetrate human skin.

After more than a decade of research, Professor of Biology Greta Binford and Research Associate and Visiting Professor Pamela Zobel-Thropp have discovered for the first time what is in the venom of these animals, and compiled evidence of the effects of their venoms on humans. The new evidence crushes that old urban legend.

In a new research paper, "Not So Dangerous After All," just published in the journal Frontiers in Evolution and Ecology, Binford and Zobel-Thropp detail their chemical analysis of pholcid (commonly known as cellar spiders or daddy long-legs) venom. Their results show that the venom is full of interesting proteins and peptides and is highly toxic to insects, but all evidence indicates it has negligible toxicity on mammals especially when compared with black widow venom, for example.

In 2014, Discover Network's hit series MythBusters took the liberty of dispelling the daddy long-legs myth with venom from the same species and overseen by Chuck Kristensen, a coauthor on this work however, until Binford's paper was published, there had been no rigorous analysis of what is in the venom of any pholcid spiders.

Funded by a grant from the National Institutes of Health since 2011, the paper details the team's diligent pursuit of solid evidence. To reach their findings, the team analyzed the composition of venom of one species of pholcid, which contains over 120 different proteins and peptides that contribute to toxicity.

"Rather than fearing daddy long-legs, we are inspired by the potential for discovery of new chemical activities in these venoms," Binford said. "They represent a cool, little studied and diverse branch of biodiversity from which we have much to learn."

To accomplish the analysis, the team relied on technologies for high-throughput sequencing and "proteomics." This work inspired building technology and a support team at Lewis & Clark for high-performance computing.

Thanks to support from Jeremy McWilliams at Lewis & Clark's Watzek Library Digital Initiatives Office, the team used the college's HPC cluster (lovingly named BLT for its three servers: bacon, lettuce, and tomato—better together) to crunch data analyzing 9 proteomes and 22 transcriptomes. The use of high-performance computing not only provided otherwise unattainable insights and discoveries, it also proved invaluable in training student-researchers.

"Having hands-on opportunity for our students to use high-performance computing expands their analytical abilities and allows them to be less limited in the scope of questions they can ask and answer," Binford said. "It also gives us the chance to teach students how to critically evaluate evidence coming from analyses of 'big data.""

Her research team included students (both current and since-graduated), collaborators from other higher-education institutions, and even one local high-school student.

"Being a part of Greta's research team was one of the greatest privileges I have had in my life," said Jennifer Mullins BA '12, who now works in healthcare administration in Western Washington. "Coming from an underprivileged background, I always felt as though I was behind my peers at Lewis & Clark. Thus when applying for the coveted position as a Roger's Fellow in the Binford Lab, I was sure I was the least likely candidate. But Greta picked me and allowed me to continue a project I had started in her lab the semester prior looking into the daddy long-legs venom myth. What floors me is she let me come up with the project on my own and it is crazy for me to think how it has come to fruition."

Binford is quick to credit all her research collaborators, including paper coauthor Chuck Kristensen, whom she jokingly calls her "venom dealer." Kristensen operates Spider Pharm, a company in Arizona that maintains myriad spider species colonies and produces venom for research and antivenom production, including the pholcidae species used in Binford's research.

Binford's spider research has appeared in the New Yorker, PBS's NOVA series and NPR's Science Friday, to name a few. In 2011, she was named Oregon Professor of the Year. An arachnologist and spider-woman through and through, Binford even has a species of spider named for her (the Austrarchaea binfordae).

Mullins said, "There are many moments that stood out in my experience working with the Binford research team—sailing in the Caribbean catching arachnids, education outreach to Dominican orphans and Haitian refugees—but what made the biggest impact on my life is just having Greta give me the chance to be part of the team. Having someone believe in you makes all the difference."

Fatal Mistake? Researchers Study Black Widow Spider Venom and 1900 Death

Cal State Fullerton spider researcher Merri Lynn Casem and her students are untangling a web of mystery surrounding the 1900 death of a construction worker bitten by a black widow spider. Did the man die from the venom of this highly poisonous spider or a fatal mistake by the doctor treating him?

The researchers are investigating the historic case of the man’s death on July 26, 1900, from a modern-day perspective of understanding the biological effects of black widow venom and the treatments he received.

The man was bitten by the spider while using an outhouse at the construction site of the first Masonic Temple, now the Parker Building, in downtown Fullerton. He was treated by Dr. George Crook Clark, one of Fullerton’s pioneer doctors and the original owner of what is now the Heritage House at the Fullerton Arboretum, located on the CSUF campus.

The researchers are working on a manuscript to describe how the physiological effects of the spider venom and the various drugs used to treat the patient may have combined to result in one of the first medically documented cases in the nation of a fatal black widow spider bite. Their work is based on an article describing the case published in the Southern California Practitioner in 1901.

“At the time, the venomous nature of the black widow was not recognized,” said Casem, chair and professor of biological science who studies the cellular and molecular biology of spider silk, as well as spider development. “Because of this, Dr. Clark would not have known the best way to treat a black widow spider bite.”

Casem’s students, biological science majors Omniya Abdelmaksoud and Sharon Chang, are studying the medicines used in the early 1900s and the physiological effects the black widow spider toxin, called alpha latrotoxin, has on the human body. The spider, whose scientific name is Latrodectus hesperus, is known for the prominent red hourglass pattern on its belly.

Chang, a double major also studying anthropology, plans to become a physician. She became interested in the research because of its relevance to the history of medicine.

“In our case study we emphasize the overlap between history and science,” said Chang, who received a research stipend from Friends of the Arboretum for the study. “Our understanding about the effects of alpha latrotoxin has changed over the past 100 years with the advancements in medicine and biology. Piecing together the knowledge we have now, with what happened back then, is an important focus of our research.”

A Deadly Spider Bite?
The physician’s treatment focused on preventing infection and relieving the patient’s extreme pain by using drugs that included potassium permanganate (an antifungal and antiseptic agent), an 8% solution of cocaine as an analgesic and morphine, Casem explained.

It was reported that the patient, whose name was George, was convinced he was going to die when his condition did not improve with treatment. He took matters into his own hands by downing several six-ounce glasses of whiskey, Casem said. When his breathing became labored and he lost consciousness, Dr. Clark attempted to revive him using ammonia and camphor inhalation.

“When that did not work, Dr. Clark injected George with strychnine and whiskey,” Casem said.

Strychnine, a lethal poison, was used as a therapeutic agent at the turn of the century. The patient died 14 hours after being bitten. The cause of death was reported as blood poisoning. After George’s death, the black widow spider was discovered in the outhouse.

While dying from a black widow bite is rare, black widow spiders remain a potential health threat due to the alpha latrotoxin protein found in their venom, Casem said. Symptoms include body pain, severe muscle cramping, nausea and abnormal heart rate. Modern treatments focus on pain relief, including the use of opioids. An antivenom can be used in severe cases.

“Alpha latrotoxin protein functions to disrupt the nervous system by forming calcium ion channels in the membranes of nerve cells. Calcium ion plays a critical role in the communication between nerve cells, so disrupting the levels of calcium in the nerve would result in ‘misfiring’ and lead to muscle contractions and pain,” Casem said.

The most recent data reveals that of the 1,015 cases of black widow spider bites recorded in 2018, there were no deaths and six patients suffered potentially life-threatening symptoms.

Casem and her students’ research concludes that while Dr. Clark followed accepted medical practice of the time for blood poisoning, some of the drugs used, such as strychnine, combined with the patient’s consumption of alcohol, could have contributed to the fatal outcome.

“Was the spider responsible, the doctor, or George himself? This research is the sort of story that can be left for the reader to decide,” Casem said.

Contact: Debra Cano Ramos, [email protected]

Merri Lynn Casem, chair and professor of biological science

Spider venom reveals new secret: Once injected into a bite wound, venom of brown recluse spider causes unexpected reaction

Venom of the brown recluse spider causes a reaction in the body that is different from what researchers previously thought, a discovery that could lead to development of new treatments for spider bites.

University of Arizona researchers led a team that has discovered that venom of spiders in the genus Loxosceles, which contains about 100 spider species including the brown recluse, produces a different chemical product in the human body than scientists believed.

The finding has implications for understanding how these spider bites affect humans and for the development of possible treatments for the bites.

One of few common spiders whose bites can have a seriously harmful effect on humans, the brown recluse has venom that contains a rare protein that can cause a blackened lesion at the site of a bite, or a much less common, but more dangerous, systemic reaction in humans.

"This is not a protein that is usually found in the venom of poisonous animals," said Matthew Cordes, an associate professor in the UA's department of chemistry and biochemistry and member of the UA BIO5 Institute who led the study, published today in the journal PLOS ONE.

The protein, once injected into a bite wound, attacks phospholipid molecules that are the major component of cell membranes. The protein acts to cleave off the head portion of the lipids, leaving behind, scientists long have assumed, a simple, linear, headless lipid molecule.

The research team has discovered that in the test tube, the venom protein causes lipids to bend into a ring structure upon the loss of the head portion, generating a cyclical chemical product that is very different than the linear molecule it was assumed to produce.

"The very first step of this whole process that leads to skin and tissue damage or systemic effects is not what we all thought it was," Cordes said.

The lipid knocks off its own head by making a ring within itself, prompted by the protein from the spider venom, Cordes explained. "Part of the outcome of the reaction, the release of the head group, is the same. So initially scientists believed that this was all that was happening, then that became established in the literature."

The research team includes Cordes Vahe Bandarian, an associate professor also in the UA's department of chemistry and biochemistry and Greta Binford, an associate professor of biology at Lewis and Clark College in Portland, Ore. who, completed her doctorate and a postdoc at the UA.

Cordes, Bandarian and Daniel Lajoie, a PhD candidate in Cordes's lab, tested venom from three species of brown recluse spiders from North and South America. Binford, an arachnologist who has traveled the world in search of the eight-legged creatures, collected the spiders, isolated their DNA and milked their venom, which was then frozen and shipped to the UA labs for analysis.

"We didn't find what we thought we were going to find," Cordes added. "We found something more interesting."

The cyclical shape of the headless molecule means that it has different chemical properties than the linear headless lipid believed to be generated by the protein, Cordes explained. The biological effects of either molecule in human membranes or insects aren't completely known, he said, but they are likely to be very different.

"We think it's something about that ring product generated by this protein that activates the immune system," Binford said.

"The properties of this cyclic molecule aren't well-known yet, but knowing that it's being produced by toxins in venoms might heighten interest," Cordes said. "Knowing how the protein is actually working and making this cyclic molecule could also lead to better insights on how to inhibit that protein."

For those who do have a reaction to the venom, the most common response is inflammation that after one to two days can develop into a dark lesion surrounding the bite site. The blackening, or necrosis, of the skin is dead skin cells, evidence of the immune system's efforts to prevent spread of the toxin by preventing blood flow to the affected area.

"Our bodies are basically committing tissue suicide," Binford said. "That can be very minor to pretty major, like losing a big chunk of skin. The only treatment in that case is usually to have a skin graft done by a plastic surgeon."

About once every five years, Binford said, someone develops a serious systemic reaction to a brown recluse bite, which can be fatal.

"If it goes systemic, then it can cause destruction of blood cells and various other effects that can in extreme cases lead to death by kidney failure or renal failure," Cordes said.

However, it is believed that the vast majority of brown recluse bites are so minor that they go unnoticed by those who were bitten.

It's not known what determines the type or severity of reaction a person is likely to get when bitten by a brown recluse, Cordes said, "but what is known is that this protein is the main cause of it."

"I think if we know how the toxin works, it opens a new door to understanding how the syndrome is initiated as well as the possibility of blocking that process."

"The discovery of this product may be crucial in understanding what exactly is going on in the human reaction," Binford said.

For the spider biologists and chemists, the work has just begun.

"These spiders have been around with this toxin for over 120 million years," Binford said. "I want to understand the full set of variation present in a single spider and across the entire genus and the activity of this compound."

"People think about the brown recluse with fear," she added. "When I think about a brown recluse or any other spider, I think about how a single spider can have 1,000 chemicals in its venom and there are about 44,000 species, so tens of millions of unique compounds in spider venom that we're in the process of discovering. We have a lot to learn about how these venom toxins work and potential for understanding new chemistry and developing new drugs or treatments."

Understanding how brown recluse venom produces harmful effects in humans is particularly relevant in Arizona, a hotbed for these spiders, Cordes said: "There are more variant species of Loxosceles here than anywhere else in the United States."

The UA-led study of brown recluse venom was supported initially by a pilot project award from the UA BIO5 Institute. Binford's venom collections were supported by a National Science Foundation Career Award.

The Chemistry of Spider Venom

Click to enlarge

Spiders are the most numerous venomous animals on the planet the number of species predicted to be in existence, 150,000, is thought to be greater than the numbers of all other venomous creatures combined. Almost all spiders, with only a few exceptions, produce venom, which serves the primary purpose of immobilising their prey. However, the content of this venom can vary wildly from species to species, and the majority are not harmful to humans. This graphic takes a look at some of the different possible components, and their roles in venoms.

Initially, spider venoms can be grouped into two broad categories: necrotic, and neurotoxic. Necrotic, or cytotoxic venoms, are those which cause cell and tissue damage after envenomation. This can lead to the appearance of inflammation, lesions, and blisters. Neurotoxic venoms, on the other hand, exert their effects on the nervous system, and interfere with signalling between neurons. In extreme cases, these can lead to respiratory and cardiac arrest. Note that some spider venoms can actually contain both necrotic and neurotoxic components.

When it comes to the venom components themselves, they’re often grouped into categories according to their molecular weights: low molecular weight compounds (<1000), peptides (1000-10000), & proteins (10000+). For different species of spider, a different one of these categories may contain the primary toxic component of the venom. Despite the huge number of different spider species, a comparatively small percentage of spider venoms have had their compositions characterised. Generally, however, they contain a huge number of compounds from all three groups.

The low molecular weight compounds consists of salts, carbohydrates, and small organic compounds such as amines, acids, and acylpolyamines. It’s thought the potassium ions in salts may assist the toxic portions of the venom in reaching their molecular targets in victims. High potassium ion concentrations can also affect the signalling between neurons in the nervous systems of insects. Amines, meanwhile, can include neurotransmitters such as serotonin and noradrenaline. These are similarly capable of interacting with an insect’s nervous system, and also aid in the spreading of the venom through the insects body.

Acylpolyamines are significant low molecular weight toxins in the venoms of some spiders, and more than 100 have now been characterised. Often, spider venoms will contain a number of different acylpolyamines, rather than just one. It’s thought that their primary purpose in venoms is to paralyse insects by blocking glutamate receptors.

Peptides are the main component in most spider venoms. On average, they’re thought to contain around 25% polypeptides by weight, and analysis has suggested that some individual venoms could harbour up to 1000 different peptides. Some contain linear, cytolytic peptides which have necrotic effects. The action of these cytolytic peptides is relatively non-specific, and they can also act synergistically with neurotoxic components. It’s also been suggested that they could aid in the external digestion of the spider’s prey.

It’s disulfide-containing peptides that are the major players in spider venoms, however. Aside from a few exceptions, in most venoms they are the major toxic component. They are more potent than the cytolytic peptides, and are also more selective in terms of their targets. These tend to be ion channels on neurons. It’s also been suggested, due to the nature of some other targets of these compounds, that some of them may have been evolved to ward off predators, rather than for insecticidal activity.

Finally, the higher molecular weight components include enzymes and larger proteins. Enzymes have an obvious role in external digestion of the spider’s prey once it’s been envenomated, and a variety of different enzymes have been identified in spider venom. Additionally, by breaking down extracellular structures, they also enable the spread of the venom. One enzyme, hyaluronidase, is also thought to be for the purpose of self-defence, as its target, hyaluronan, is found in vertebrates but not invertebrates..

High molecular weight proteins are fairly uncommon as toxic components of the venom. However, there is a notable exception: that of Widow spiders, which include the Black Widow Spider. Their venom contains toxins called latrotoxins, which have been the subject of many studies. One such toxin, alpha-latrotoxin, binds to nerve terminals and causes huge release of neurotransmitters into synapses, blocking signal transmission. The effects of a Black Widow spider bite can last up to 5 days, though they rarely kill.

You might wonder why scientists have spent so much time researching spider venoms, other than just out of curiosity. The demand for better insecticides, which are capable of exerting effects on specific insects without having any detrimental effects on other wildlife, means that we are looking to spider venoms as a potential source of insecticidal compounds. More widely, their chemical diversity also makes them candidates for drug discovery programs.

As mentioned at the outset, the venom of the majority of spiders is largely harmless to humans. There are, though, a few notable exceptions. Widow, Recluse, Wandering, and Funnel-Web spiders are all considered to pose a threat to human health.

Why You Need Not Fear the Poor, Misunderstood Brown Recluse Spider

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The brown recluse spider's reputation vastly exceeds its reality. Note the three pairs of eyes: That's the best way to identify these guys. Photo: Rick Vetter

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It’s hard to think of a critter that inspires as much hyperbolic hysteria as the brown recluse spider. They're pretty much universally hated. If you believe the tales, these small arachnids are biting people all day, every day, producing massive, stinking flesh-craters that require months of intensive care and perhaps a prosthetic appendage. Sometimes, it seems these spiders have nothing better to do than hunker down in dark corners throughout North America, waiting for tender human skin to present itself.

Though there are strands of truth in the hype, on the whole, it’s bunk.

William V. Stoecker/Swanson & Vetter, New England Journal of Medicine, 2005

It is true that some of the spider’s bites lead to necrotic skin lesions, but around 10 percent of them. The others (like the one at right), aren't that bad. The brown recluse (Loxosceles reclusa) only lives in a few states – basically, the warmer ones between the Rockies and the Appalachians. And they don’t really want to bite you. It’s actually not that easy for them.

The brown recluse reality is obscured by a number of factors, not the least of which involves gnarly internet photos. First, spiders in general are easy to fear, and misinformation about this species in particular abounds. Second, bite wound statistics are clouded by misreporting. Third, many other conditions can be misdiagnosed as brown recluse bites (like MRSA and fungal infections). Lastly, many other spiders (and insects) are mistaken for brown recluses.

“There is a really strong emotional and psychological aspect to the brown recluse,” said arachnologist Rick Vetter, now retired from the University of California, Riverside.

Inspired by the comments left on a story we did about the silk of a closely related recluse spider, the South American brown recluse, we decided to take a close look at our own continent's most despised brown spider and the myths surrounding it.

First, a truth: Brown recluse bites can be bad. "They are a potentially dangerous spider," said Vetter, who has spent decades studying the brown spiders. “They’re not harmless,” he says. “But the reputation they have garnered in this country is just amazing.”

Cases of Mistaken Identity

Much of Vetter’s work has involved verifying the identity of spiders purported to be brown recluses. In 2005, Vetter published the results of a nationwide appeal for spider specimens suspected to be L. reclusa: Please send me the spiders you think are brown recluses, and tell me where you're from. He received 1,773 specimens, from 49 states. Less than 20 percent -- 324 -- were brown recluses. All but four of those came from states with endemic brown recluse populations.

"An initial goal of this study was to determine the spider characteristics that people were misconstruing as that of a brown recluse," he wrote. "It became evident early in the study that all that was required was some brown [body] coloration and eight legs."

'People jump at the chance to hate spiders. It’s easier to vilify them than to adore their biology and natural history.'

Along the way, Vetter realized that authorities -- such as poison control centers and physicians -- aren't much better at identifying the brown recluse. Even trained entomologists can get it wrong.

In 2009, Vetter took a close look at 38 arachnids incorrectly identified as recluses by 35 different authorities such as “physicians, entomologists, pest control operators – people you’d think would have reliable opinions,” Vetter said. Misidentifications included a solifuge (which isn't even a spider), a grass spider pulled from a patient’s ear, and a desert grass spider that had bitten a young boy.

Part of the problem is that the brown recluse is small and brown and about the size of a quarter -- like many other arachnids and insects. The best way to identify a brown recluse is to count its eyes: They’re among a few species of North American spiders that have six eyes instead of eight, arranged in three pairs of two.

But your typical spider-squisher isn’t going to get in a spider’s face with a magnifying glass and count its eyes. Some people may try to find the marking most commonly described as identifying a brown recluse: a violin shape on the spider's head, oriented with the violin’s neck pointing toward the spider’s butt.

However, people are incredibly good at "seeing" violin markings on every portion of a spider’s body, Vetter says, which means this marking isn't an especially helpful diagnostic.

A Disconnect Between Bite Reports and Sightings

, the Chilean recluse whose silk we reported on earlier, that live near Los Angeles.

Small, brown spiders run around pretty much everywhere on Earth. But the brown recluse only lives in a few states between the Rocky Mountains and the Appalachians.

"Arkansas and Missouri are the two states where they're very, very dense," Vetter said. Kansas, Oklahoma, the western portions of Tennessee and Kentucky, the southern parts of Indiana and Illinois, and the northeastern parts of Texas round out the recluse's range.

Though the spiders can travel around – maybe in luggage, or freight – it’s uncommon to find a brown recluse outside its native range. Still, reports of brown recluse bites from states outside the recluse range abound. For example, Vetter and his colleagues studied six years of brown recluse bite records, derived from three poison control centers in Florida. A total of 844 brown recluse bites were reported. But in 100 years of arachnological data, only 70 recluse spiders (not all of them brown recluses) have been found in the entire state.

Vetter took a similar look at Georgia, a state on the margins of the recluse’s range. Theyɽ asked that any and all suspected recluse specimens be submitted for identification. More than 1,000 spiders came in, but only 19 were brown recluses. In the state's arachnological history -- derived from searching through museum collections, historical records, websites, and storage buildings in parks -- there were only about 100 verified brown recluse sightings, mostly in the northwest portion of the state. But a five-year dataset from the Georgia Poison Center contained 963 reports of brown recluse spider bites.

Similar patterns exist in northwest states – Washington, Oregon, and Idaho – that are far outside the spider’s range, and other states on the spiders’ margins, like Indiana.

Cases of Mistaken Diagnosis

Vetter and other experts suspect that the brown recluse bite diagnosis is a popular catch-all for situations where the cause of a skin lesion can’t be easily identified. True, there are many things that can cause a nasty-looking flesh wound -- but the brown recluse diagnosis carries an unlikely charisma. "If you get a bacterial infection, do you tell anyone about it? Of course not," Vetter said. "But if you think you got a brown recluse bite, you tell everybody! You put it in your Christmas letter."

This is NOT a brown recluse bite. It's anthrax, misdiagnosed as a brown recluse bite.

From Swanson and Vetter, New England Journal of Medicine, 2005

Over the years, Vetter and his colleagues have compiled a list of about 40 things that can masquerade as recluse bites: bacterial infections, viral infections and fungal infections poison oak and poison ivy thermal burns, chemical burns bad reactions to blood thinners herpes.

“People want to believe [the culprit] is a spider species,” said entomologist Chris Buddle of McGill University, noting that it's easier to blame a spider than something less familiar, like drug-resistant bacteria.

Most physicians don't have a lot of experience discriminating between a recluse bite and something like necrotizing Staphylococcus. And even if a patient brings in a spider for identification, it's unlikely the ER doctor has been trained to ID a brown recluse.

There are some ways in which brown recluse bites are different from many other wounds, however. A raised, reddish and wet wound is likely not a recluse bite, Vetter says. Recluse venom destroys small blood vessels and causes them to constrict, turning the area around the bite white, or purple, or blue. Fluids can't flow to the area, and it sinks a little, and dries out.

In reality, just 10 percent of recluse bites require medical attention. The rest look like little pimples or mosquito bites or something else that doesn't merit a trip to the emergency room, and they heal by themselves. But the reality about bite statistics doesn't seem to matter. Even when faced with numbers and geographic distribution maps, people still cling tightly to their beliefs about the recluse and its arachnid malfeasance.

The Persistence of Myth

It is true that brown recluses like hiding in dark corners. They're nocturnal and shy away from daylight and, sometimes, the outdoors. Hence the name. But they are not waiting in these dark corners to bite you. It's possible to live with the spiders and not get bitten. Take the rather extreme example of a Kansas family that lived for six years in a house infested by 2,055 brown recluse spiders. Total bites: Zero.

In fact, the spiders’ fangs are too short and small to bite through pajamas or socks, and really only sturdy enough to puncture thin skin. Most bites occur when people roll over on the spiders in the night, or try to wear a shoe the spider has moved into. "Biting is a response to being crushed, but theyɽ much rather try and get away," Vetter said.

'If you get a bacterial infection, do you tell anyone about it? Of course not. But if you think you got a brown recluse bite, you tell everybody'

But the idea that something hazardous lurks in the dark, out of sight behind a toilet or inside a shoe, is a potent source of fear. The idea lodges in the psyche and is difficult to shake loose – especially when fed by popular media and peers. “The press has, by and large, painted spiders in a negative light,” Buddle said. “People jump at the chance to hate spiders. It’s easier to vilify them than to adore their biology and natural history.”

Things that are potentially harmful, move erratically, unpredictably, and sometimes quickly, are easy to fear. Spiders fall into this category, says psychologist Helena Purkis, who has studied arachnophobia and fear of snakes at the University of Queensland, Australia. And then, when people fear something, they expect it to be associated with bad things.

“The truth is, bad things happen to us all the time, and it’s completely random,” said entomologist Gwen Pearson, author of the WIRED Science Blog, Charismatic Minifauna. But being able to blame a nasty skin lesion on a spider is more satisfying than acknowledging that a necrotic crater has emerged on your arm for no identifiable reason, she says.

Purkis described an experiment in which shocks were randomly paired with either pictures of flowers, or pictures of spiders. “People report that spiders, but not the flowers, were predictive of shocks – even when the presentations were completely random,” she said.

Searching for patterns in the noise is one of the ways human brains handle the overwhelming amount of stimuli in the world -- but it also leads to misperceptions. Here, our fallibility is in our tendency to filter new information and remember facts more easily if they are consistent with our beliefs, Purkis says. This means that you could hear one bad story about a brown recluse bite and 10 stories about how the spiders aren’t so bad, and guess which one will stick?

Atrax robustus & Hadronyche formidabilis

Male Sydney funnel-web spider
(Photo V Draffin) Female Sydney funnel-web spider
(Photo V Draffin)


There are several species of funnel web spider found throughout Australia. The best known of these is the Sydney funnel web spider, Atrax robustus. The male of this species (in the picture on the left) is Australia's most dangerous spider, and is capable of causing death in as little as 15 minutes. The Sydney funnel web is a large, black aggressive spider with large powerful fangs. It lives in burrows or crevices in rocks or around house foundations, lining the burrows with silk. Colonies of more than 100 spiders may be found. The male spiders in particular tend to wander into houses in the summer, especially in wet weather. It is unusual amongst spiders in that the male appears to be more dangerous than the female. It is also of note that the venom appears to particularly affect primates, whereas other mammals are relatively resistant.

Several other funnel web spiders species have been described throughout Australia, including the northern or tree-dwelling funnel web (Hadronyche formidabilis), found in northern New South Wales and southern Queensland, as well as species found in Victoria, South Australia and Tasmania .


A. robustus is found only within a 160 km radius of Sydney, although related species have been described all along the east coast of Australia, and one of these, the northern or tree-dwelling funnel web spider (Hadronyche fomidabilis), has been shown to be dangerous to man.

Female Hadronyche formidabilis
(Photo V.Draffin)


There is little information on the toxicity of most of these spiders' venoms, and the danger they may pose to man. In most cases of bites by A robustus, little venom is injected and no symptoms develop. None the less, first aid should be promptly applied and medical attention sought without delay. If envenomation has occurred, the bite site may be extremely painful, although tissue necrosis is not seen. There is some evidence that prolonged immobilisation of venom in the tissues may lead to inactivation. Symptoms can develop within minutes if effective first aid is not employed. Symptoms and signs of envenomation include: Numbness around the mouth and spasms of the tongue, nausea and vomiting, abdominal pain, acute gastric dilatation, profuse sweating, salivation, lacrimation, piloerection.

Northern or tree dwelling funnel web spider: Female (left), male (centre) and spiderlings (right)
(Photos P.Walker)

How Can You Prevent Spider Bites?

Many people spend their whole lives sharing their living spaces with venomous spiders, and yet they are never bitten. Spiders usually only bite as a last resort. Even so, these bites can be serious, and if you are motivated to reduce your risk even further, there are ways to do so:

  • Keep your bed away from the wall. This leaves spiders with fewer ways to climb up the bed while you sleep. Keep the area under your bed clear so spiders have fewer ways to climb.
  • Be careful when you pull things from storage. Undisturbed areas are inviting hunting grounds for spiders.
  • When you put things in storage, close them in zipped plastic bags, taped cardboard boxes and other secured containers. This can help keep spiders out.
  • Many spiders are attracted to undisturbed wood piles and junk, so keep your yard clear.
  • Spiders often bite when someone puts on a piece of clothing that has been left undisturbed for weeks or months. If you're putting on a pair of shoes or a jacket that's been left in storage, shake the clothes out first.
  • Pesticides are largely useless against spider infestations, and may do more harm than good. A better way to control spider populations is through sticky traps.