Bad Bugs of Summer: Black Widows

05.23.2011 |

Much of what you've probably heard about black widows is wrong. Know your enemy.

It’s hard to think of an arthropod with a worse reputation than the black widow. Heck, the term is even used to describe serial killers – and it doesn’t get much worse than that. We’ve already covered mosquitoes, ticks and carpenter bees in our “bad bugs” series, but any conversation about bugs people hate has to include spiders. So let’s talk about black widows.

Most people don’t know much about black widows – and some of what they think they know is wrong. For example, while their venom is dangerous, a black widow bite is generally not lethal to humans – especially for healthy adults. And, while “everybody knows” that black widow females devour males after mating, that ain’t necessarily so. Spiders are predators, so it does happen, but  most males don’t die after mating – they hit it and quit it (so to speak).

You likely know the familiar image of female black widows: black spiders with globelike abdomens, emblazoned with a red hourglass on the back. Not all black widows look like that. Some black widows, particularly male or immature ones (I will not comment on this grouping), have stripe-like markings on the abdomen. And the hourglass shape on the females can be whitish or yellow, rather than red. Furthermore, not all black widows are black.

One reason for the confusion about what black widows may look like stems from the fact that, when we talk about “black widows,” we could actually be talking about any of several species. There are 31 different species of “widow” spiders around the world, all in the genus Latrodectus. Of those 31, five can be found in the United States – and three in North Carolina (where I’m writing this post, and where I’ll focus my attention).

The most common species in NC are the northern black widow (L. variolus) and the southern black widow (L. mactans). The so-called brown widow (L. geometricus) is a relative newcomer to the area, and still somewhat uncommon.

Around here, you’ll see southern black widows more often, because they like to build their webs close to the ground and in enclosed spaces – like woodpiles. Northern black widows are also fairly common, but they prefer a higher perch (look out when you’re changing the bulb in your porch light).

As a rule, black widows (whatever the species) use relatively small webs to catch their prey, though they will also snag prey that simply comes too close. Be comforted by the fact that black widows want to avoid you. Humans, after all, are much, much bigger than spiders.

However, black widows will set up house in places that make man-spider interactions a distinct possibility. Black widows eat insects and, occasionally, other arachnids. They’ll go where the food is, such as the aforementioned woodpile or porch light – both of which tend to draw insects of one variety or another. And, if put on the defensive, black widows will bite you.

The cleaner and tidier you keep your woodpile, shed, garage, etc., the less likely you are to have black widows (or insects and spiders in general). But it’s not feasible to eliminate the possibility altogether. So be careful. Wear gloves when you’re bringing in wood, or reaching into places that you can’t see.

If you are bitten, and you’re sure it was a black widow, don’t panic. A healthy adult may suffer mild symptoms – or no symptoms at all. But if you do begin to feel ill, call a doctor. And if you have started feeling very ill, go to an urgent care facility (you may want to have someone drive you). However, if the person who has been bitten is a child, a pregnant woman, or someone in poor health, you should seek medical attention immediately.

Check out the other posts in our series on summer pests: mosquitoes, ticks, carpenter bees and horse flies.

Note: Many thanks to Dr. Mike Waldvogel, extension specialist and associate professor of entomology, and Dave Stephan, insect identification specialist at NC State, for taking the time to talk to me about black widows. Any errors in the above post are mine and mine alone.



12 Responses to “Bad Bugs of Summer: Black Widows”

  1. [...] Check out the other posts in our series on summer pests: mosquitoes, ticks, horse flies and black widows. [...]

  2. [...] Check out the other posts in our series on summer pests: mosquitoes, ticks, carpenter bees and black widows. [...]

  3. Nirmal says:

    So Black Widow cant kill ? None of 31 species ?

  4. Matt Shipman says:

    Many of the “widow” species are capable of killing humans. However, they are unlikely to kill a healthy adult. They are particularly dangerous to infants, children, the elderly and those who are in poor health. They can also pose serious health problems to pregnant women.

    It’s important not to downplay the health risk posed by bites from Latrodectus species. However, it’s also important not to have a panic attack every time you see one.

  5. [...] year I wrote a series of posts about critters we love to hate: mosquitoes, ticks, horseflies, black widows and carpenter bees. With the arrival of spring, I decided to pick up where I left off. First up: [...]

  6. [...] Check out the other posts in our series on summer pests: mosquitoes, horse flies, carpenter bees and black widows. [...]

  7. [...] Check out the other posts in our series on summer pests: horse flies, ticks, carpenter bees and black widows. [...]

  8. Thank you Matt for your article. I am here in Asheville and just moved into a new home and found a relatively large spider in my office. Like many, I am a little apprehensive of big spiders (small ones are no problem). And I make it a point to release them outdoors. But this one, is quite large and because my husband has seen a black widow near the base of our house outdoors, I jumped to the thought that it that one who got inside.

    As I write this post, I have her in a glass jar soon to be released outside. In the meantime, I wanted to find out more and ran into your article. Thank you for writing it and for dissolving some misconceptions about black widows.

    Cheers,
    Sophia

  9. Matt Shipman says:

    I’m glad you found it useful, Sophia! Please share it with anyone you think might be interested. We’ve tackled a lot of creepy critters, because we think they are less intimidating when you know a bit about them. You can see more profiles of “bad bugs” (and other random science questions) here: http://web.ncsu.edu/abstract/tag/explainer/page/2/

  10. Danielle says:

    I just found a Northern Black Widow inside our TKD Studio today. Had no idea that Black Widows could have marking on their backs, as opposed to underneath. Out of curiosity, is anyone doing anything to protect the species? Are there any places doing research on them, that we could take the spiders to?

  11. [...] far as the correctness goes. There are 5 different Widow species in the US, and Black Widow bites are not lethal to humans. In fact, as of 2011, there are no known reported deaths from black widow bites in the US.  Black [...]

  12. […] written dozens of blog posts inspired by questions my children have asked me: Are black widows dangerous? What colors do bees see? How do bees make honey? (My kids like […]

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