Black Widow or False Black Widow?

some kind of widow spider

I have a family of widow-type spiders living in my outdoor worm bin. I like spiders and all they do around the garden, and have a no kill policy toward them in general. This particular situation, however, has had me a teeny bit nervous. They hang out on the underside of the lid of the worm bin for the most part, though I’ve seen them on the surface of the worm compost once or twice. Obviously my concern is that I will touch one when opening or closing the bin, or while burying my kitchen waste.

Believing these spiders to be black widows, my options have been either to be very attentive while around the worm bin–or to roll out the vacuum. So far I’ve opted for being careful.

The thing about these spiders is that they lack the identifying spots on their abdomens, but I remembered being told somewhere that not all types show the red marks, and that males never do. Was this true? Were there other types of spiders that looked like this? After weeks of tip-toeing around the worm bin, I finally got around to doing some research. My conclusions are not conclusive, so I’m coming to you, dear readers, for help.

Wikipedia’s entry confuses me a bit:

Not all adult black widows exhibit the red hourglass on the ventrum underside or top of the abdomen — some may have a pair of red spots or have no marking at all. Female black widows often exhibit various red markings on the dorsal or top side of the abdomen, commonly two red spots. However, black widow young are believed to have at least some sort of marking on their abdomens. Adult male black widows are half the size of the females, and are usually gray or brown rather than black and red; while they may sometimes have an hourglass marking on their ventral abdomen, it is usually yellow or white, not red. Variation in specifics by species and by gender is great; any spider exhibiting a red hourglass or a pair of large red round spots on the ventral abdomen with an otherwise black shiny body is an adult female black widow.

Here is how I read this: Not all adults display an hourglass…but females often display some sort of red mark. Young and males may or may not have some kind of mark, but not red…but be careful! Variations by species and gender are significant. If you see a black spider with red markings, be very, very afraid. That there is definitely a female black widow. But really, there’s no guarantees here that other less flashy spiders aren’t some kind of dangerous, either.

This is not reassuring.

But then on the handy page Frequently Encountered Spiders in California, I learned about the False black widow.

Another European invasive, this spider seems to be displacing our native black widows in urban areas.  This spider is roughly the same size and shape as a black widow, but is brown with a faint purple sheen.

I like this false black widow option a lot. The false widows don’t have a dangerous sting.

The spiders in my box are pretty shy, but insofar as I can tell, they are all sort of an eggplant color–not that true, bad-ass black of a classic widow. Nor have I seen any red marks. (That doesn’t mean that big mama with her red marks isn’t hiding somewhere.)

So, from this not-so-great photo, can anyone tell me if this particular spider might be a false widow, Steatoda grossa, or a male black widow, Latrodectus hesperus? It’s about 1/2 inch in size.

UPDATE 5/10:  After reviewing the evidence, I believe this is a false black widow. However, my trouble are not over, because it turns out that they do have a venomous bite, apparently somewhat like a mild black widow bite. Here’s the bite intensity scoop according to UC IPM: black widows: obviously bad; brown widows: mild; false black widows: moderate.

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44 Comments

  1. The fact that you’ve got a “family” leads me to believe that this isn’t a black widow, which are usually solitary. We just found one yesterday in a plant tray and have been doing a bit of research ourselves.

  2. Not to scare you too much (I like the idea of a false black widow too), but we live in the SoCal area and have lots of Brown Widows. They look quite a bit like your picture. They are not black at all, but they do most certainly still have the red markings on the underside of their abdomen. Have you been able to see the underside of these guys you have? I do agree with the above post. If you really have a “family” of them, unless there is one momma with several little tiny babies, they probably aren’t widows. They tend to be very territorial.

    • I’ve not seen red marks on any so far. The pic on the post shows the underside of one, for instance.

      However, re: territoriality I haven’t seen the other family members recently. There were tiny babies at one point, and I’ve seen up to 3 adult spiders one time or another hanging out in different parts of the bin, but lately–as far as I can tell– it seems down to the one in the pic. Did she polish off the others? (shiver)

  3. All pictures I’ve seen of male black widow spiders look totally different from the females, so I’m fairly sure the spider you have is not a male black widow. I had an infestation of black widows at my old house (killed about a dozen over approx 2 years) but the only ones I have ever seen have been super shiny black with the red hourglass on their underside or two red spots on their back. And I’ve never seen more than one at a time. I personally would exterminate them and remove any doubt. Lol.

  4. I had one of these in my outdoor worm bin too. I squished it. I have an amnesty policy for all non-scary looking spiders, but scary ones get squished

  5. Black widows will have a non-sticky strong web, do not live in colonies (very territorial), and do not like to be far away from the ground. If the spiders are on your lid, they must be about 3-4 feet off of the ground? These are probably not black widows. Also, BW’s do not like to be in areas with heavy traffic. If you are disturbing their nests on a regular basis, they will move somewhere else.
    I routinely do a “Black widow hunt” of my house and yard every month. I kill approximately 5 each time (my whole neighborhood is infested). I have never found them to be more than an inch off of the ground. They like to live in the cracks between the foundation and the house, or between pipes and the house. They only come out at night when the weather heats up. There is always some sort of red on the abdomen of the females, and the males are brown with yellow on the abdomen. Good hunting with a headlamp, insecticide (to slow them down), and my spider killing stick.
    P.S. I do allow all other spiders to live :)

    • I live in Oklahoma far from all of you but I read where you said black widows stay close to the ground. We had one this year on the outside of my sons bedroom window screen far from the ground, she had three giant yellowish egg sacks hanging out with her on the screen. We saw it from our living room window, my daughter actually spotted it and told us about it. Needless to say, my husband took our wasp spray that sprays up to 20 feet and soaked her and her eggs with it then finished her off.

  6. Yup, the sticky, messy web is pretty tell tale of a widow, I have seen “families” of them inhabiting an area, large webs with 5 or 6 spiders (they probably know who’s web is who’s and where the property lines are…….) In the interest of safety, I’d say it’s time to serve an eviction notice!

  7. False Black Widow – we’ve got TONS of them at our place too. Used to kill with reckless abandon, then started doing some reading on them when we had kids, and now let them live for the most part – unless of course we meet in a less than manly way, then its still squish immediately.

    Based on – the size factor (though male black widows are smaller, so not the smoking gun perse…), brownish-purple coloration and lack of spots another, as well as the “non-solitary” behavior.

    If it walks like a duck, quacks like a duck :)

    Our place is full of crazy random spiders… though we recently unleashed a whole squad of spider killers at the Light homestead – the chickens are putting a hurt on the spider populations. I almost feel bad for them, then I think about all those fabulous orange yolks, and I feel better. :)

  8. We’re in Whittier, also have a ton of what we thought were brown widows. A ton. Hiding in the kale and other various plants and bushes, around the patios, around the worm bin…we leave them be.
    I had previously noticed red markings, so after some research we concluded they were brown widows. But now, looking at your pic, I wonder if all of ours actually have the telltale red marking…body wise, our spiders look like your pic. I have become so used to them that I guess I don’t pay attention anymore to red spots or not.

    As for black widows….we do see them on the rare occasion. But hiding in more secluded/quiet recesses.

    Note on the brown widows…. We’ve read that they are not as dangerous, and conversely, just a dangerous as the black ones.

  9. If you want a firm identification I would recommend calling your county extension service to find a phone number and email address for an extension insect specialist. You should be able to have a conversation with that person or send several photos and get a good id on these critters.

  10. First of all, I would not depend on Wikipedia for poisonous spider ID. At least go to and .edu site. I do agree with Andrea about the spiders, but I would take or send the spider in for identification to a county extension office.

    Do you want to be bit by something that is just a bit less dangerous as BW? I do not want spiders anyplace I handle quite often. These spiders are close to the ground, the ground of their world, the worm box.

    That said, I did let a spider live in a window and another behind the microwave. Both were catching their body weight in fruit flies, every day. They were helping me.

    When I had company, I would scare them away and vacuum their webs. The next day, the spiders were back at work, having made new webs and catching more insects.

    One of the problems, I have heard, of insect bites other than the spider “venom” is the introduction of germs/bacteria into the opening they make. You really don’t need an infection on your hand.

  11. I’ve never done any real research but I do find unmistakable Black Widow spiders around my house with some frequency.

    What I’ve heard is that the toxic spiders of whatever variety will weave a chaotic web. If I see those, I put on my gloves and tear them out. If I see the Black Widows I shudder inside and squish them. Dark places and around my cactus are where I see them most often.

    I haven’t knowingly encountered a Brown Widow. Did you say they are benign?

    • Brown widows are not benign, but false black widows, which are brownish, are okay. It’s confusing.

  12. When I was 7, my family moved to the Okanagan and someone told me that they had black widow spiders. I did not sleep the first night there, moving from room to room, imagining black widows crawling in to my sleeping bag to kill me. Since that time we have seen loads of black widows. We had a HUGE female make her web in the garage window and you should have seen the amount of moth carcasses that piled up on that ledge. We co-existed with her quite peacefully, we respected her space and she respected ours. Your spider does not look like any black widow I have ever seen, but I am no expert.

  13. That doesn’t look like a black widow because of the color.

    The black widow’s I’ve seen are a shiny black and the females are big! They are native, so I do think there’s a reason for them to be here. They are being squeezed out by the Brown Widow (from Africa) that is smaller and has an orange hourglass on its abdomen. BTW, they are reputed to be more venomous than the native black widows.

    These spiders like to hang upside down, so it’s easy to identify them. Their web is chaotic and very sticky so if you see that you know there’s one hanging around. They also come out at dusk and hang upside down (mentioned that already). They like the underside of patio furniture because it’s close to the ground.

    We have Greenleaf spray our garden and building perimeter with a non-toxic repellent for fleas and haven’t seen them since. I happen to think they are beautiful and very elegant and only killed one once. It curled up into a ball to protect itself which made me feel really bad. If they were so dangerous I think we’d here of many more accounts.

    I would opt for a live and let live situation.

    • ps. The brown widow egg sac looks like a WWII underwater bomb, a round globe with spikes. If you see that in the web, you know you have brown widows.

    • Re: not hearing about many bites. That’s true. I was thinking about that, too. I know several people who’ve had brown recluse bites (nasty!) but I don’t know anyone who’s been bitten by a black widow.

      Does anyone here have any stories?

    • I always think of them as being like halloween decorations– like the plastic rings I used to get as party favors when I was a kid. They are kind of like the Ur-Spider.

      I saw an unmistakable black widow recently somewhere else, and she was just so shiny/black/sinister/big that I thought that the spiders in my box couldn’t be the same breed.

  14. Black widow webs are very distinctive–they are total chaos and very sticky. The generally go between 2 surfaces–a chair leg and the bottom of the seat, bike tire and frame, toy dump truck and the ground, and unused smoker and the ground, the house and the patio, the stacking concrete blocks in the short wall. We have black widows and brown widows (or at least, the brown widow egg cases, so I assume the spiders are here somewhere). We only see the black widows at dusk, they hide all day. They are generally quite large–and can be HUGE.

    • Yeah, these are a little small. Not really small, but just not impressively large.

  15. The messy web is a great indicator. To control spider populations encourage wasps as they love spiders. A wasp sting is no problem compared to a Black Widow bite.

    • Apparently all widow-type spiders make chaotic webs, including the false black widows.

      We have lots of wasps, actually! These I count as another …um…challenging insect resident of our yard whom I give wide berth.

    • thanks! UC IPM is a great resource for bug questions of all sorts. Should have thought of them.

  16. False black widow. We have tons and tons of both black and false widows at our house in Davis. In our experience, black widows like very dry environments, so unless your worm bin is very dry, I wouldn’t expect to find them there. False widows will tolerate moist environments. Black widows build super strong webs (almost like fishing line)-that’s how we initially ID them. False widows’ webs may look chaotic, but won’t be nearly as strong. Also, female black widows will be a very glossy dark black, not a muted brown like the one in your picture. Immature and male black widows look altogether different from the classic black widow momma shape. In twelve years living with these gals ALL over our yard (http://banyans-end.blogspot.com/2012/05/black-widow-factory.html), none of us have ever been bitten–we are just very careful and aware.

    • Thanks for the reassurance — and that’s one scary post! Widow in the shoe? shuddddder.

  17. I generally have a no kill policy when it comes to spiders but the widow family means I bust out the shop van without guilt. Their webs tend to be very taut and just have a few strands. In my garden if it resembles a widow type spider I don’t think twice. My $.02

    • Thanks! That makes me feel so much better about the bazillion brown widows and egg sacks I find in all the kids backyard toys. (so much for them not liking places that are regularly disturbed!)

  18. I live in Australia and spiders here aren’t a problem so i think you’ll be fine whatever that spider is.
    If you really want to know, get someone to volunteer to be bitten.
    If they live, its not too dangerous :)

  19. routinely find a big female black widow in my greenhouse. Sometimes in the garden tool shed HIGH OFF THE GROUND; absolutely red hourglass on her belly and all. Know where they hang out. choose just to be careful. Figure they are there because of a plentiful food supply. also figure that much of their plentiful food supply would be insects that are NOT wanted otherwise. Also welcome snakes for the same reason, with the exception of rattlers who get moved elsewhere. Figure I’m as much invading their territory as they are invading mine. They see me as a danger to their well being too.

  20. Found this post because we just adopted a worm bin from someone living on the other side of the island (Oahu) and there are at least 5 of these same spiders living around the lid and the cardboard I put in the bin.

    We decided to leave them in but tonight I got freaked out seeing several brown sacs..some of which seemed heavily guarded. So I. Started fantasizing about 5000 baby spiders hatching and got freaked out.

    What did you find out and what did you do?

    I would love for them to eat fruit flies and roaches that find their way in but never saw any of these in their web… it didn’t even look like they had a web at all!

  21. Brown widows have only been around a few years mainly since 2010. There is ongoing research and you can actually send in specimens to help with the research. BUT here in Alabama we have them EVERYWHERE. They usually have a hunters orange hourglass on their underside! Whoever said their bite isn’t bad lied to you!! It isn’t quite as bad as a black widow but it is much worse than our other venomous spider in Alabama the brown recluse! If brown widows are around your children’s toys you should kill them! There has not been enough research on their bites….especially when it comes to children! The bite also leaves an ugly scar….much worse than my brown recluse scar!

  22. Also……black widows and brown widows love mailboxes, windows, and edges of garbage cans which are high off the ground……so don’t take the advice that if its up high its not a black widow…..

  23. Your spider is a species of Steatoda. One species, Steatoda grossa is the “false widow,” but yours is not that one (longer legs in the S. grossa spider). Yours is a smaller Steatoda species, but because they tend to resemble each other I can’t go beyond the genus.

    I consider them harmless and nothing to worry about. Here’s some more information on these spiders: http://bugguide.net/node/view/6926

  24. On the note I read many comments on black widows being territorial I think it depends on the season. Around fall time between my house ground based air conditioning unit there is a huge assortment spiders and just huge tangle of webs including black widows and other species I have yet to identify I have collected some of the spiders and put them in jars in my freezer the ones I have collected I know are two black widow females and I have either two false widow female spiders or two unmarked widows. And i have read many places there are black widows without marks.

  25. I think the spiders may be there because the heat put off by the unit. because once winter hits and the AC is completely out of use the spiders are gone.but the spiders are willing to share space for a benefit of warmth or maybe a excess food supply.

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