- Author: Rick Vetter
If you were to ask an audience of more than a few people if they or anyone they know has ever seen or been bitten by a brown recluse spider in California, many hands would be raised. This is quite remarkable because the brown recluse spider has NEVER established breeding populations in California!
The myth of the brown recluse has been generated and sustained by:
- Physician misdiagnoses (where many skin lesions of diverse non-spider origin are blamed on a non-existent spider)
- Media articles that report claims of horrendous bite injury without proof of spider involvement
- Misidentification of harmless brown spiders as brown recluses by the general public as well as "authorities" who lack adequate spider identification skills
Brown recluse mythology is persistent throughout North America, even in places such as Alaska and Canada, which are far from where the spider is actually found. In some places, it is easy to argue against this myth because no recluse spiders have ever been found there. For California, this argument is less definitive because the state's south eastern deserts are home to several related native species such as the desert recluse spider (a different species than the brown recluse).
Additionally, in urban Los Angeles County, there have been rare records of isolated populations of the Chilean recluse spider. However, the native desert species occur where few people live and the Chilean recluse has only been found in commercial buildings, never in homes. There have been no confirmed bites by this non-native Chilean recluse since it was originally found in Los Angeles in the late 1930s. There have been rare findings of brown recluse in California, but these have occurred as hitchhikers in moving boxes from other areas of the country and the spider was destroyed after locating.
Although there are some recluse spiders in limited areas within California, this does not explain the hundreds (and maybe thousands) of brown recluse bite misdiagnoses made in California each year. In a study mapping out such misdiagnoses vs. known populations of recluse spiders in California, more than 95% of the purported brown recluse bites occurred in urban areas where the spiders are not known to inhabit.
For many decades throughout North America, it has been readily assumed by the medical community that many skin lesions resulted from brown recluse spider envenomation. However, recent research shows that most of these lesions are unrelated to spiders. Causes include some medical conditions that are much worse than any recluse bite would be.
One real danger of such a recluse bite misdiagnosis is that the actual causal condition will not respond to recluse bite remedy, allowing the real condition to continue on unabated, worsening and potentially leading to death. Some of these afflictions misdiagnosed as recluse bite include: cancer, leukemia, lymphoma, Lyme disease, bacterial infections, anthrax, adverse reaction to blood thinners, poison ivy, poison oak, chemical burn, thermal burn, and more. One of the most common conditions misdiagnosed as a spider bite is the bacterial infections caused by methicillin-resistant Staphylococcus aureus(MRSA).
To find out more about the different species of recluse spiders, identifying features of the brown recluse, and other spiders commonly mistaken for recluses, see the recently updated Pest Notes: Brown Recluse and Other Recluse Spiders on the UC IPM website.
[Article originally published as "The Brown Recluse Spider Does NOT Occur in California" in the Spring 2019 issue of the Retail Nursery and Garden Center IPM News.]
- Author: Rick Vetter
[Reblog from Pests in the Urban Landscape]
If you were to ask an audience of more than a few people if they or anyone they know has ever seen or been bitten by a brown recluse spider in California, many hands would be raised. This is quite remarkable because the brown recluse spider has NEVER established breeding populations in California!
The myth of the brown recluse has been generated and sustained by:
- Physician misdiagnoses (where many skin lesions of diverse non-spider origin are blamed on a non-existent spider)
- Media articles that report claims of horrendous bite injury without proof of spider involvement
- Misidentification of harmless brown spiders as brown recluses by the general public as well as "authorities" who lack adequate spider identification skills
Brown recluse mythology is persistent throughout North America, even in places such as Alaska and Canada, which are far from where the spider is actually found. In some places, it is easy to argue against this myth because no recluse spiders have ever been found there. For California, this argument is less definitive because the state's south eastern deserts are home to several related native species such as the desert recluse spider (a different species than the brown recluse).
Additionally, in urban Los Angeles County, there have been rare records of isolated populations of the Chilean recluse spider. However, the native desert species occur where few people live and the Chilean recluse has only been found in commercial buildings, never in homes. There have been no confirmed bites by this non-native Chilean recluse since it was originally found in Los Angeles in the late 1930s. There have been rare findings of brown recluse in California, but these have occurred as hitchhikers in moving boxes from other areas of the country and the spider was destroyed after locating.
Although there are some recluse spiders in limited areas within California, this does not explain the hundreds (and maybe thousands) of brown recluse bite misdiagnoses made in California each year. In a study mapping out such misdiagnoses vs. known populations of recluse spiders in California, more than 95% of the purported brown recluse bites occurred in urban areas where the spiders are not known to inhabit.
For many decades throughout North America, it has been readily assumed by the medical community that many skin lesions resulted from brown recluse spider envenomation. However, recent research shows that most of these lesions are unrelated to spiders. Causes include some medical conditions that are much worse than any recluse bite would be.
One real danger of such a recluse bite misdiagnosis is that the actual causal condition will not respond to recluse bite remedy, allowing the real condition to continue on unabated, worsening and potentially leading to death. Some of these afflictions misdiagnosed as recluse bite include: cancer, leukemia, lymphoma, Lyme disease, bacterial infections, anthrax, adverse reaction to blood thinners, poison ivy, poison oak, chemical burn, thermal burn, and more. One of the most common conditions misdiagnosed as a spider bite is the bacterial infections caused by methicillin-resistant Staphylococcus aureus (MRSA).
To find out more about the different species of recluse spiders, identifying features of the brown recluse, and other spiders commonly mistaken for recluses, see the recently updated Pest Notes: Brown Recluse and Other Recluse Spiders on the UC IPM website.
[Article originally published as "The Brown Recluse Spider Does NOT Occur in California" in the Spring 2019 issue of the Retail Nursery and Garden Center IPM News.]
/span>- Author: Jeannette E. Warnert
![Rangeland infested with yellow starthistle. Rangeland infested with yellow starthistle.](http://ucanr.org/blogs/anrnews/blogfiles/8282.jpg)
Invasive yellow starthistle aims to take over the world
Sacramento Bee, Sam McManis
Reporter Sam McManis likened yellow starthistle to an overexposed Hollywood star, presenting the bulk of the story as a mock interview with the invasive weed. An editor's note said the article was based on interviews with Joseph M. DiTomaso of the Weed Science Program at UC Davis and Wendy West, coordinator of the yellow starthistle Leading Edge Project for the UC Cooperative Extension. Additional information was provided by the California Invasive Plant Council and the University of California Integrated Pest Management Program.
Spider scientists creep up on elusive prey
Los Angeles Times, Nicole Santa Cruz
UC Riverside scientist Rick Vetter was the primary source for a Los Angeles Times story on brown widow spiders. The exotic spider is "spreading like wildfire" across Southern California, Vetter said. "It's not that big of a deal, but people see the word 'widow' in a name and freak out completely."
Rick Vetter explains brown widow spider identification in the ANR video below:
- Author: Jeannette E. Warnert
Brown widow spiders are beginning to displace the more dangerous black widows in some parts of California, according to a story in the Riverside Press-Enterprise.
The brown widow spider, a native of South Africa, made its first American home in Florida. It became established in Southern California in the early 2000s and its range continues to expand. As of 2009, the spider was known in Los Angeles, Orange and San Diego counties, but as of 2010, it has shown up in Santa Barbara and Sacramento counties.
"They're very prolific," said Rick Vetter, a UC Riverside urban entomologist who is documenting the species' spread in California. "Where you might find six or seven black widows in a backyard, now you find 100 brown widows."
The mottled tan, brown and gray spiders - like their black cousins - carry the signature hourglass marking on the abdomen, however the brown widow's mark is orange or yellow instead of red. They can also be distinguished by their egg sacs; the brown widow's has spiky protrusions.
Vetter told Press-Enterprise reporter Janet Zimmerman there is concern the brown widow will make its way to California's Central Valley, where they could have an impact on the agricultural industry.
"People don't want the spiders shipped around on their produce," Vetter said.
Although brown widows may congregate in greater numbers and their venom is more potent, the spiders pose less risk than black widows. Brown widows are less likely to bite. Instead they curl up when disturbed and do not defend their egg sacs. When they do bite, they release less venom than black widows.
"Most of the bites recorded so far have been very mild," such as pain and redness at the bite site, Vetter was quoted in the story.
Vetter asks that California residents outside of LA, Orange and Ventura counties send him samples of brown widows they find so he can track their spread. For more information, see Vetter's webpage.
![Brown widow Brown widow](/blogs/blogcore/blogfiles/5003.jpg)