10 Fascinating Facts About Black Widow Spiders

black widow spider on web
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Black widow spiders are feared for their potent venom, and rightfully so, to some degree. But much of what you think is true about the black widow is probably more myth than fact.

Interesting Things About Black Widow Spiders

These 10 fascinating facts about black widow spiders will teach you how to identify them, how they behave, and how to minimize your risk of being bitten.

They Aren't Always Black

When most people talk about the black widow spider, they likely think they're referring to a particular spider species. But in the U.S. alone, there are three different kinds of black widows (northern, southern, and western).

And although we tend to refer to all members of the genus Lactrodectus as black widows, widow spiders aren't always black. There are 31 species of Lactrodectus spiders worldwide. In the U.S., these include a brown widow and a red widow.

Only Adult Females Inflict Dangerous Bites

Female widow spiders are larger than males. It is believed, therefore, that female black widows can penetrate vertebrate skin more effectively than males and inject more venom when they bite.

Nearly all medically significant black widow bites are inflicted by female spiders. Male widow spiders and spiderlings are rarely a cause for concern, and some experts even say they don't bite.

Females Rarely Eat Their Mates

Lactrodectus spiders are widely thought to practice sexual cannibalism, where the smaller male is sacrificed after mating. In fact, this belief is so widespread the term "black widow" has become synonymous for femme fatale, a kind of seductress who lures men with the intention of bringing harm to them.

But studies show that such behavior is actually quite rare in widow spiders in the wild, and even uncommon among captive spiders. Sexual cannibalism is actually practiced by quite a few insects and spiders and is not unique to the often maligned black widow.

Most Can Be Identified by a Red Hourglass Marking

Nearly all black widow females bear a distinct hourglass-shaped marking on the underside of the abdomen. In most species, the hourglass is bright red or orange, in sharp contrast to its shiny black abdomen.

The hourglass may be incomplete, with a break in the middle, in certain species like the northern black widow (Lactrodectus variolus). However, the red widow, Lactrodectus bishopi, does not have an hourglass marking, so be mindful that not all widow spiders are identified by this feature.

Spiderlings Don't Resemble Adult Black Widows

Widow spider nymphs are mostly white when they hatch from the egg sac. As they undergo successive molts, the spiderlings gradually darken in color, from tan to gray, usually with white or beige markings.

Female spiderlings take longer to reach maturity than their brothers but eventually turn dark black and red. So that drab, pale little spider you found just might be a widow spider, albeit an immature one.

They Make Cobwebs

Black widow spiders belong to the spider family Theridiidae, commonly called the cobweb spiders. These spiders, black widows included, construct sticky, irregular silk webs to ensnare their prey.

Members of this spider family are also referred to as comb-foot spiders because they have a row of bristles on their back legs to help them wrap silk around their prey. But no need to worry. Although they are closely related to the house spiders building cobwebs in the corners of your home, black widows rarely come indoors.

Females Have Poor Eyesight

Black widows rely on their silk webs to "see" what's going on around them because they can't see very well. The black widow female usually hides in a hole or crevice and builds her web as an extension of her hiding spot. From the safety of her retreat, she can feel the vibrations of her web when either prey or predator comes in contact with the silk threads.

Male widow spiders looking for mates use this to their advantage. The male black widow will cut and rearrange the female's web, making it difficult for her to sense what's happening, before carefully approaching her to mate.

Their Venom Is 15 Times as Toxic as a Prairie Rattlesnake's

Widow spiders do pack a powerful punch of neurotoxins in their venom. By volume, Lactrodectus venom is an extremely toxic mix of poisons capable of causing muscle cramps, severe pain, hypertension, weakness and sweating in bite victims.

But black widow spiders are significantly smaller than rattlesnakes, and they're built for subduing other small invertebrates, not large mammals like people. When a black widow spider bites a person, the volume of neurotoxins injected in the victim is small. 

Their Bites Are Rarely Fatal

Although black widow bites can be painful and require medical treatment, they are very rarely fatal. In fact, the majority of black widow bites cause only mild symptoms, and many bite victims don't even realize they were bitten.

In a review of over 23,000 documented Lactrodectus envenomation cases that occurred in the U.S. from 2000 to 2008, the study authors noted that not a single death occurred as a result of a black widow bite. Only 1.4% of bite victims suffered "major effects" of black widow venom.

Most Bites Used to Occur in Outhouses

Black widows don't often invade homes, but they do like to inhabit human-built structures like sheds, barns, and outhouses. And unfortunately for those who lived before the water closet was commonplace, black widows like to retreat under the seats of outdoor privies, perhaps because the smell attracts so many delicious flies for them to catch.


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Hadley, Debbie. "10 Fascinating Facts About Black Widow Spiders." ThoughtCo, Sep. 9, 2021, thoughtco.com/fascinating-facts-about-black-widow-spiders-1968549. Hadley, Debbie. (2021, September 9). 10 Fascinating Facts About Black Widow Spiders. Retrieved from https://www.thoughtco.com/fascinating-facts-about-black-widow-spiders-1968549 Hadley, Debbie. "10 Fascinating Facts About Black Widow Spiders." ThoughtCo. https://www.thoughtco.com/fascinating-facts-about-black-widow-spiders-1968549 (accessed March 20, 2023).