Good news, everyone! Brown widow spiders have arrived

Oct 06 2010 Published by under Biology & Environment

Black widow hanging out on my planter

I don't like spiders. I know, deep down, that they are unlikely to hurt me, and that they eat flies and other pesty insects.  Even so, I have a visceral reaction when a  spider crawls into my vicinity. I'm pretty much OK with spiders that stay outside (although stumbling on a big one, like the one Zuska found on her rain barrel might cause me pause1).

But black widow spiders (Latrodectus hesperus) are another  story. They are indeed venomous and their bite is supposed to be quite painful. Just reading about the symptoms makes me cringe:

Severe muscle pain and cramps may develop in the first two hours. Severe cramps are usually first felt in the back, shoulders, abdomen and thighs. Other symptoms include weakness, sweating, headache, anxiety, itching, nausea, vomiting, difficult breathing and increased blood pressure.

But no one in the U.S. has died from a black widow bite in over a decade, so it's not that bad, right?

Fortunately, black widows rarely end up inside the house. Instead they make their webs in dark nooks and crannies, usually only coming out after dark or if they are disturbed.  Their amorphous webs - straight from a haunted house - are pretty easy to spot and sweep away.  They leave me alone and I pretty much leave them alone.

Brown is apparently the "New Black"

But then one of the local newspapers had to run an article ensured to freak me out a bit: "Brown Widows Now in Inland Area"

Brown widows (Latrodectus geometricus) are cousins to the  black widow. They are more drably colored than the black widow, with brown bodies and an orange or yellow hourglass on the abdomen.  Brown widows are originally from  South Africa, and have been working their way west from Florida for the past 10 years or so. Only recently have they appeared in Inland Southern California.

How do brown widow spiders compare to black widows? According to the article:

  • Brown widows are more abundant than black widows. According to Rick Vetter, who studies spiders at UC Riverside, "Where you might find six or seven black widows in a backyard, now you find 100 brown widows."
  • Brown widow venom is twice as toxic as black widow venom.
  • Brown widows live in more open locations - such as under patio chairs and in chain link fences - than black widows

They sound pretty nasty, right?  I'll admit I went out to my patio and made sure there weren't any webs on my plastic patio chairs shortly after reading the article.

But the real story - easy to overlook among all the scary-sounding description2 - is that brown widows are much less likely to bite than black widows, and when they do, they don't inject as much venom. That means that they aren't actually considered to be dangerous.

As the UCR Spider Research site explains:

A South African medical journal reports on the bites of 15 brown widows in humans (Muller 1993) . Only two symptoms of brown widow envenomation were reported in the majority of bite victims: 1) pain while being bitten and 2) a mark where the bite occurred. That's it. Not much more. The bite of the brown widow is about the same as any non-poisonous spider. It hurts and leaves a little mark on the skin. It is no big deal. There are none of the serious, protracted symptoms that one would exhibit when bitten by a black widow.

So the appearance of the brown widow really is good news, at least from the public safety perspective, because they may be displacing the black widow, which is dangerous.

I'll still be happier if I never run in to one.

If you want to help track the spread of the brown widow spider in California, you can mail any brown widows you find outside of San Diego, Orange, or Los Angeles County to Rick Vetter at UC Riverside.

If you are in Los Angeles County, you can also participate in the Los Angeles Spider Survey, sponsored by the Natural History Museum of Los Angeles.

---

1. Where "pause" means that I get my husband to move it away from any outdoor equipment I want to use.

2. Especially when the article concludes with advice from an entomologist with the National Pest Management Association who advises (not surprisingly) dusting with pesticides or calling an exterminator. "Kill them all" seems a bit over-the-top advice for non-dangerous spiders.

Top image: By me.

Bottom image: thumbnail of graphic from the Press-Enterprise article "Brown Widows Now in Inland Area". Click the thumbnail to see the full-sized image.

22 responses so far

  • Harry Case says:

    Good article. The only thing I would add is that the black widows bite is actually fairly mild at the time it happens. Some people don't even know they've been bitten. But they sure know it later! http://www.pestcontrolcenter.com/blog

  • Dan Cummings says:

    be careful out there

  • [...] yesterday’s post about black and brown widows made you want to learn more about venomous spiders, you should check out DN Lee’s latest post [...]

  • hdcase says:

    The one point you are overlooking here is the bigger concern that this is yet another exotic species that is displacing native ones. No one knows how much damage it could do to beneficial organisms and our ecology in general.

    [Edited to remove irrelevant link. You are free to link your name to your web site.]

  • Michael says:

    Probably the reason for this UCR Spider Research is that because brown widow spiders are smaller than the black ones to penetrate the human skin and inject enough venom. But if we're going to look at the actual danger that these brown widows can cause, they're more dangerous than black. Source: brownwidowspider.net

  • jimmy johnson says:

    There are 100's of brown widows where I live in S.E.Georgia. Brunswick,to be exact!!

  • Hi, just wanted to tell you, I loved this post. It was helpful. Keep on posting!

  • whiney says:

    I was bitten by a brown widow. It was a terrible experience. :(

  • ellie says:

    I live in Ny in Dutchess county which is pretty rural. At present I have a brown widow that has spun a web on the outside of my picture window. I have pictures although it was difficult to get a clear one.I think the climate in ny is to harsh for them. However there she is.

  • vanessa says:

    I was just met my first brown widow in my childrens closet not a gomeanod experience. They r mean looking...

  • vanessa says:

    I live in anaheim

  • vanessa says:

    Sorry everyone my cell is going crazy anyway my buddy from terminix told me what it was

  • Eula Casselman says:

    Plenty of the brown widows in Texas, Odessa/Midland area.

  • Mike says:

    We have about 200 of these in my backyard (Norwalk California) Havent seen a black widow in months, They love my patio planters, and the deck chairs/tables. They will drop to the floor when disturbed as a defense. And have a Spiked white eggsack. Making it easy to locate and destroy. Every night for two weeks i have gone outside with a fly swatter and taken out about 20 i find, and every night another 20 take the places of ones killed. Havent been bit, even with one landing on my bare foot. Invasive and producing like mad, but they dont bother me too much.

  • Broskee says:

    I found a Brown widow in my house hanging from the A/C vent in my haul way .its black with black and brown legs yellow design on its back and orange hour glass on its belly ... I live in phoenix Arizona

  • Two hours after I was bit(on New Year's Eve,2013) by a huge brown widow I was in pure misery, headache, hot and sweaty all over, had to go to bed I felt so bad. Should have gone to urgent care, which I did two days later. She bit me on the neck, then migrated to inside my t-shirt in the front where I found her, caught her and killed her. I managed to save one of the legs and could identify her from that. You all say the bite is not as painful as black widow. I work in the garden all the time, have been bitten by black widows several times with not the pain and suffering I experienced with this one. I was on muscle relaxants and naproxen for two weeks and still felt pain. My neck muscles are still tight and sore and it is ten weeks later.
    I am not happy they have migrated to California and now have to be doubly careful in the shed and garage and when my grandkids are around.

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  • Ed says:

    I have a comment for all those who worry about the invasions of exotic species displacing natives. People used to try to stop all forest fires, until they finally figured out that occasional fires were actually good for the environment. If you believe in evolution, why don't you accept this as survival of the fittest? Evolution goes on everyday people. Species come, and species go. If the brown widow is replacing the black widow, I'm not sure the black widow deserves to continue living in our backyards. How's that for food for thought?

  • Ed says:

    Oh yeah, and for the record, in 2014, the brown widow is now appearing in my backyard near Macon, so it's moving pretty fast. I don't think we can consider it an exotic species anymore, although it truly is an invasive one.

  • kahr74 says:

    Im sorry, but the brown widow is poisonous, just not as poisonous as our native black widow. It is not good for it to be here, there are more docile, yes, not as poisonous, but will infest your yard, house faster than any black widow.
    I have lived in san juaquin county most of my life and have already seen more brown widows than black. Black widows are extremely poisonous, but on the ground are notthe fastest due to there large behind, yes Iif the have egg sack, they will be more aggressive and can move extremely fast in there web. At least ten time ive ran into a black widow web, thats usually below knees. They run away faster than I do.
    My cousin was bit by walking through a field with birkenstocks and was bit. By 24 hrs he was sick, stomach cramping , sweating, . He thought it was stomach flu, by 48 hrs, he was running a fever almost 105.0 had to be admitted. They gave him anti venom. Recovered within two days. I find black widows to be beautiful. But I dont want to share my home,. Black widows kill mosquitoes. Weve had more deaths from west nile than black widow. So you decide, but brown widows are like allowing farrets to go wild in california. Not good.

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