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Most Dangerous Spiders in California

Updated on August 20, 2017
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Since completing university, Paul has worked as a bookseller, librarian, and freelance writer. Born in the UK, he now lives in Florida.

A female Western Black Widow.  The female of the species is much larger than the male and has by far the most venomous bite.  She is jet black in color and has the distinctive hour glass marking on her lower abdomen, which is typically red.
A female Western Black Widow. The female of the species is much larger than the male and has by far the most venomous bite. She is jet black in color and has the distinctive hour glass marking on her lower abdomen, which is typically red. | Source

There are two types of spider that are capable of delivering venomous bites of note in California, qualifying them as being the most dangerous: widows and recluses.

Although threatening to humans, death from a widow bite is rare nowadays thanks to the development of anti-venom. Pain and discomfort is most likely to be the worst result of a bite, and often there may be little or no effects.

Recluse bites tend to be rarer than widow ones in the state, thanks to the desert recluse not generally living in close proximity to humans and Chilean recluses only being present in a few limited areas of the south. The most common species of recluse spider found in the USA, the brown recluse, does not inhabit California.

Widows and recluses can potentially be found both indoors and outdoors. You can lower the chances of getting bitten by one of these spiders by:

  • Being able to clearly identify each type of spider
  • Having an understanding of the sorts of places where you are likely to encounter them
  • Taking sensible precautions, such as wearing gloves when reaching into places where you cannot see, such as high shelves and dark corners, particularly in sheds and outhouses.
  • It is also advisable to shake out old clothes, towels, linen, etc. that hasn’t been used for a period of time, before you put them on to wear.

Below is a full description of each spider type, including their common habitats, behaviors, and venomous bites.

Widow Spiders in California

As its name suggests, the Western Black Widow (Latrodectus Hesperus) is found across western regions of the USA.

The females are the ones to look out for when it comes to venomous bites. They are jet black in color and have the distinctive red hourglass markings on their lower abdomen (although in some cases, the hour glass can be yellow in color, or even occasionally white).

The males are brown to orange in color and generally pretty harmless. The female eating of the male after mating is actually rare in this species and the male often gets to mate numerous times.

Despite their fearsome reputation, widow spiders are timid and will usually run away rather than bite, if they feel threatened.  The only exceptions are when the female is guarding her eggs, or when the spider is pinched against or feels squashed.
Despite their fearsome reputation, widow spiders are timid and will usually run away rather than bite, if they feel threatened. The only exceptions are when the female is guarding her eggs, or when the spider is pinched against or feels squashed. | Source

Widows are nocturnal and build messy looking, three-dimensional webs. They will commonly hang upside down near the center and when they sense an insect getting caught (usually through vibration, rather than by vision), they run over and bite the insect, before covering it in their silk.

Male Western Widow Spider.  The male is much smaller and lacks the powerful venomous bite of the female.  Despite her reputation, the female widow rarely eats the male after copulation, and the male often gets to mate several times over.
Male Western Widow Spider. The male is much smaller and lacks the powerful venomous bite of the female. Despite her reputation, the female widow rarely eats the male after copulation, and the male often gets to mate several times over. | Source

Widows have a fearsome reputation when it comes to venomous bites, but the truth is that you are unlikely to die when bitten unless you are particularly old and frail, or a young child. Treatment should always be sought straightaway, however.

It should also be noted that Widows are generally timid and will almost always try to run away if they feel threatened. The only exceptions to this are when a female spider is guarding her eggs, or when a Widow is accidentally pinched or pressed against - this can occur when someone puts on old clothing such as a glove or shoe and there is a spider inside it, or if someone is reaching or feeling around in an area where a widow is dwelling, such as a high shelf or dark recess.

Widow Bites

Note that the bite itself may feel like just a small pin prick at the time, or may not even be noticed. Symptoms don’t usually start until 1 to 3 hours after the poisonous bite and may include:

  • Severe pain
  • Headache
  • Muscle and abdominal cramps
  • Nausea
  • Convulsions and tremors
  • Excessive sweating
  • Lesions in the bite area
  • Vomiting
  • Unconsciousness

To start with, the venom just affects the area of the bite, but then it gradually it travels around the body via the lymphatic system, before getting into the bloodstream. Symptoms normally persist for 3 – 5 days maximum. It is extremely unlikely that a Widow bite will be fatal if the victim receives medical treatment.

The Chilean recluse is generally considered to be one of the most venomous species of all the recluse spiders.  Although, as its name implies, it is native to South America, it is known to have established itself in the Los Angeles area.
The Chilean recluse is generally considered to be one of the most venomous species of all the recluse spiders. Although, as its name implies, it is native to South America, it is known to have established itself in the Los Angeles area. | Source

Recluse Spiders in California

The desert recluse is the commonest type of recluse to be found in California. This species inhabits the eastern desert regions of the state. Bites from these spiders are rare as they are not usually found in high population areas, so encounters with humans are limited.

There are also Chilean recluses in the Los Angeles area of California. These are considered one of the more toxic species of the recluse family.

(Although brown recluses are common in many other parts of the U.S., they don't live in California.)

As their names suggests, recluse spiders are not aggressive by nature. They tend to bite only when pressed against human skin, for example when an article of clothing is put on which a recluse is living in.

Recluse spiders are generally timid and seldom seen by humans. Bites usually occur when someone reaches or feels around in an area that they can’t see, or when someone puts on an old item of clothing that the spider was hiding in.

Recluse Bites

The effects of a recluse bite can vary enormously, from virtually no effect, all the way up to death (in very rare instances).

Symptoms of a bite typically start between 2 and 6 hours afterwards and can include:

  • Blistering
  • Severe pain
  • Chills
  • Fever
  • Nausea
  • Necrosis at the site of the bite
  • Lesions

Unfortunately, there is no effective antivenom for recluse bites, but medical care should still be found as swiftly as possible.

It should also be noted that most recluse bites are unremarkable.

Recluse bites can vary from an unremarkable bite with mild skin irritation, to severe skin necrosis.  Deep gangrenous wounds can develop and leave deep scars.  Death from a recluse bite is extremely rare however.
Recluse bites can vary from an unremarkable bite with mild skin irritation, to severe skin necrosis. Deep gangrenous wounds can develop and leave deep scars. Death from a recluse bite is extremely rare however. | Source

You can best avoid a recluse bite by:

  • Not leaving clothes, gloves, shoes lying around on the floor, if possible, and shaking them out before you put them on.
  • Not reaching into areas where you can’t see, especially shelves and recesses in sheds and outhouses.
  • Recluses are not naturally aggressive but will react aggressively if they feel that their life is threatened, or they are trapped.

Scarring from a recluse bite after four months.  Recluse spiders are the sole genus that we know to cause necrotic bites in people. The layers of skin die and slough away to leave an ulcer.  Most bites are unremarkable though.
Scarring from a recluse bite after four months. Recluse spiders are the sole genus that we know to cause necrotic bites in people. The layers of skin die and slough away to leave an ulcer. Most bites are unremarkable though. | Source

Sources

© 2013 Paul Goodman

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    • profile image

      shannon 12 days ago

      I live in San Jose California and there is an abundant population of brown recluse spiders I know many people who were hospitalized for their bites. They may have not originally been a native species I don't know but they are definitely here now.

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      herbie 2 weeks ago

      Anyone here who says that they, or that someone they know got bit by a brown recluse in California, doesn't know wtf they are talking about. THERE ARE NO POPULATIONS OF BROWN RECLUSE SPIDERS IN CALIFORNIA. I understand how convinced you are, and what the doctor said, or how the wound looked exactly or felt exactly like a recluse bite. Or how the symptoms were exactly like a recluse, etc. etc. etc. But the science and facts are that you were mistaken. Sorry.

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      Neversaynever74 6 weeks ago

      I don't understand how you can say there are no Brown Recluse spiders in Northern California. They have the name Recluse for a reason. I live in Lodi Ca, hour away from Sacramento and my husband doesnt construction and was under a building and was bit by a Brown Recluse. Not just Recluse, it got in his boot . He was is in the worst pain I have ever seen him in. It was bright red with cellulitis was actually turning into liquid. They even had a specialist come in to confirm the bite. It was a Brown Recluse he called it ( Loxosceles reclusa, Sicariidae (formerly placed in a family "Loxoscelidae") This is what he wrote in chart and discharge papers. He had to go back everyday. So he wouldn't lose his leg. They said it is very rare . They get a couple of cases a year. Remember new species are discovered everyday all over the world. Your gonna say that you are 100% absolutely positive they don't reside in North. California. Yet where I live summers reach 110° We have tons of Black Widows. Now Brown Widow's. Brown Widows were only in Southern California, till about three years ago. They actually a threat to our Beautiful Black Widow. Black Widows are not aggressive. In fact they will actually run away and in most cases not even waste poison on a human. Only when threatened or pinched . Do more research. North America, the black widows commonly known as southern (Latrodectus mactans), western (Latrodectus hesperus), and northern (Latrodectus variolus) can be found in the United States, as well as parts of southern Canada – particularly in the Okanagan Valley of British Columbia, as can the "gray" or "brown widow ...

    • profile image

      LaVerne 2 months ago

      Most recently, my church sister, Celine has been off work now for a few months after she went into cardiac arrest and mearly had her leg amputated from tbe bite of a recluse spider.

      While concluding the burial ceremony for her Aunt; as mourners were leaving, Celine said she remembered watching the spider move about during the service but refocused her attention on the ceremony and she saw it again as she got up to leave and tripped and had fallen near THE AREA of the spider. She was helped up and remembers not seeing the spider again after her fall.

      Well turns out...that spider got on her clothing and crawled under her pants and bit her leg a short time after her fall.

      BECAUSE SHE WAS A BIG PERSON weighing nearly 350lbs she suffered many organ failure issues and stayed in hospital 2 months and now walks with a cain.

      She lives in the Bay Area of CA. She was hospitilized at Highland Hospital.

      I live also in Bay Area and am witness to seeing them and black widows in my suburban community in my back yard sheds and wood piles. I see some very ugly and scary spider in my home as well and so far not one of the two venomous ones. Celine recommends peppermint oil to clean walls, floors, and window (and cracks) along with keeping a tidy home throughout so they do not feel welcomed. I am scared since this has happened to Celine.

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      Devin 2 months ago

      I live in Northern CA and a friend of mine was bit by a brown recluse. It was in an old pair of gloves in the basement of his home, which he put on without shaking out. He lost the tip of his finger to necrosis...

      So you can say there are no recluses in CA, but you would be wrong. There are always exceptions.

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      Logic 2 months ago

      As per UC Riverside's research, there are probably no significant, established populations of brown recluse in Cali. The vast majority, if not the totality, of supposed brown recluse bites occurring in the state are probably bites from another species of recluse (the Chilean recluse bite, for example, is particularly nasty and can cause severe necrosis and require hospitalization). Many commenters report the identification made by a physician as definitive, but a physician is not an entomologist! They probably properly identify a spider as a recluse, but their expertise is not in differentiating among all the species of recluse. Brown recluse is the one that everyone's heard of, so that's going to be the one most commonly named. Having said that, all these pronouncements that no one could have ever seen a brown recluse in Cali are equally absurd. The amount of human and vehicular travel into the state is astronomical. It's conceivable that several brown recluses periodically come across state lines--in someone's luggage, in cargo, ...etc. You can't dismiss an account with 100% certainty just because the probability that it's accurate is low. OK, you all can go back to drooling on yourselves now.

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      John Logothetis 2 months ago

      I got bitten by a brown recluse in L.A. We flew it to the hospital where it died shortly after it bit me. Very scary.

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      Jim 2 months ago

      Sorry Tom, UCR doesn't have the staff to look around all of California, what a joke. They didn't find any in their search, but they are not the pinnacle of researchers lol.

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      Tom 3 months ago

      There are no brown recluse spiders in CA, however there are recluse spiders. The Arizona Recluse, Baja Recluse, Chilean Recluse, Desert Recluse, Martha's Recluse, and Russell's Recluse can all be found in certain parts of California. Although they are not brown recluse they are very similar and do have the same type of venom.

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      RRuiz 3 months ago

      My husband and I were both bitten by recluse spiders in San Diego. It was documented and photographed by our physician. My husband got the worst of it but both of us suffered necrosis and staph. Our condo was infested with them in our closet and they were found in our clothes. We still have the scars. They do exist in CA.

    • profile image

      Disbelieve 3 months ago

      Who died? Your dad or the doctor?

      And i hope you are kidding

    • profile image

      Canureed 3 months ago

      I think if you believe everything you read or hear on the internet... Then come buy some authentic Big Foot pictures from me.

      I too have had friends claim they seen them or have been bitten by them. Creatures do migrate. More often then not things get misidentified and myths become facts. Anyone can write a story. Visit a University, speak to a person in that field. Call a pest control guy.

    • profile image

      Spider Hunter 3 months ago

      One post someone tells the story of something personal the next post someone tells that person they are lying. I want to play. My father was a teacher who was bit by a brown recluse in La Habra California. He went to the docs and they told him there are no recluse spiders in CA. He died.

    • profile image

      Aidan Sullivan 3 months ago

      No way there have only 10 BROWN recluse spiders caught and they were probably bought by shipments to California from the mid west there other reculse here but not brown reculse and no way two teachers were bit in California

    • profile image

      edie 3 months ago

      I know 2 teachers who were bitten by brown recluse spiders. They both spent time in the hospital and said they they has abcesses on internal organs.

    • profile image

      James Deathe 3 months ago

      There are no recluses in california.

      http://spiders.ucr.edu/myth.html

    • profile image

      Michele 3 months ago

      Sorry bust your bubble but I've been bitten by one almost died and almost lost my finger and I live in California so don't tell me

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      Erica 4 months ago

      Sorry....they DO exist in nor cal. My boss in Pollock Pines was bit in the calf, was flown to UCSF, had to have a lot of tissue and muscle removed, hospitalized quite awhile and most of his back calf was permanently gone. They had the spider and it WAS identified as a brown recluse. Granted this was a long time ago (early 90s) but they are seen at times up there.

    • profile image

      brian lowdown 4 months ago

      they never hitch rides on trucks or all the daily cars,they check them at the arizona ,california border...also i think summers are a bit warmer with drought....vallejo ca and also desert areas have had brown recluse..i bet you can find on youtube...also call the ca pest control..the boa constrictor wasn't supposed to migrate to places they are now either.

    • profile image

      Sara 4 months ago

      Two quick things- my MIL was bit years ago by a brown recluse in Petaluma, CA. She became very ill and was hospitalized at petaluma Valley Hospital. I believe that there are some in NorCal.

      Secondly, I can on here to research in regards to who to talk to about spiders in our area. I came across one in my yard that I am pretty sure was a Brown Widow, and I have never seen one in our area. I heard that they had made their way to SoCal, but have never heard of them in NorCal. Any suggestions?

    • profile image

      Not really in cali BUT.... 4 months ago

      My friend found one in California when doing a bug collecting project for college in orange county. There was a journal paper published on it and everything. That said the reason the paper was published was because they aren't really found in California so it was a big deal.

    • profile image

      pat fox 6 months ago

      one of the nations best known spider doctors, also a well know author of all about spiders book, had a standing bet of $25.000 dollars, if some one in calif. filmed and authenticated a brown recluse spider and brought it in , no takers after 2 years, offer canceled, that was 2012

    • profile image

      Tom 6 months ago

      The video:

      Clean and repacking brown recluse spider bite;

      Look up the mnemonic, NOT RECLUSE,

      It's not,

      (R)ed,

      (E)levated

      (C)hronic

      NOT RECLUSE—A Mnemonic Device to Avoid False Diagnoses of Brown Recluse Spider Bites

      Authors William V. Stoecker, Richard S. Vetter, Jonathan A. Dyer

      Journal JAMA Dermatology

    • profile image

      Tom 6 months ago

      No Brown Recluse in California ....!!!!

      Look up:

      UCR Spiders

      That's:

      University of California, Riverside, Myth of the Brown Recluse

      Tony Tee, check it out and learn how to identify a Brown Recluse.

      Scott, you took the spider to the medical center and they identified it as a brown recluse ....???? So the doctors are also entomologists ....????

      Ryan, maybe you should be doing the research ....!!!

      NorCal girl, you should contact UC Riverside and tell them about your evidence.... !!!

    • profile image

      Ralph 6 months ago

      If you do some research, there are populations of recluse spiders in the southern deserts of California. But they are not the brown recluse. They could be the desert recluse or the Arizona recluse. They are related but are not the brown recluse.

    • profile image

      Dan 7 months ago

      Def seen em in California

    • profile image

      NorCal girl 7 months ago

      I have personally seen brown recluses and so has my dad. I know for a fact there are some here. Maybe not big populations but they are here. I am not miss identifying them either.

    • profile image

      Scott 8 months ago

      I got bit in 2001 by a recluse while in bed in san diego the bite and spider were identified by Balboa naval medical center so i do believe there just might be recluses in socal

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      Mark 8 months ago

      I live in so cal. Once had a server pain in the leg. When I looked it was a large red rash with a small cut. A day later it swelled up and the small cut grew very large. 7 months later I still have a puffy scare. Does that sound like a recluse bite? I look at Google images and it was similar to a recluse, about twice the size of a black widow bite. What do you guys think?

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      exterminator 8 months ago

      Sorry but you are wrong. I am a licensed exterminator who is in the field every day. If you don't believe me, do a google search. The pest control industry, US government & ALL entomolgist/arachnologist agree that there isn't a brown recluse population in California.

      If you are the cynical type (its a coverup!) consider this. Have you ever seen a pest control ad in California for brown recluses? Seems like a pretty big money maker considering the fear-mongering & hysteria... but legally we cannot treat for a target pest if that target pest doesn't exist in our area.

      Think about it and do your own research, don't trust the testimony of that guy at a bar who swears his uncle/neighbor/ex-roommate knew a guy who knew a guy who saw one.

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      Ryan 9 months ago

      Esteban Vildoso actually they have migrated or been brought over to California, in recent years, we used to only worry about widows but now we have the recluse as well, maybe before talking down to someone who gives an informative article do a little research to see if the info you have is still viable.

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      Tony Tee!! 9 months ago

      I actually live in Petaluma ca, and work for the garbage company in the north bay and I come across brown recluse spiders, co workers run into them and Heard stories of them being in homes in Santa Rosa as well!!

    • profile image

      Esteban Vildoso 9 months ago

      Why are you talking about brown recluse spider's they don't live in California.

    • Anna Marie Bowman profile image

      Anna Marie Bowman 4 years ago from Florida

      I lived in Arizona for four years, and encountered a few Black Widow's during my time, and after seeing the pictures and video of the Brown Recluse, I am pretty sure I came across one of those, as well. Nasty little creatures! Very useful!