There aren’t many spiders in the US that are considered deadly, and the most notorious among these is the black widow. However, most of what you’ve been told about black widows is actually wrong.
This is a very complicated topic, so grab some snacks, sit back, and let’s take a look at all three species of black widows in the US. We’ll discuss their differences, how deadly they actually are, and how to get rid of black widow spiders safely.
Getting to Know Black Widow Spiders
You know all those iconic images of a black spider with a red hourglass under her abdomen? That’s actually only one of several species of black widows, each of which are very different.
In fact, the genus Latrodectus has 34 individual species, all known as widow spiders. Several of these are referred to as black widow spiders. Three species of black widow spider live in the US, so we’ll start with a description of each.
Northern Black Widow (Latrodectus variolus)
The northern widow is native to the mid-Atlantic states and has been slowly spreading out over the decades. Their exact range is unknown, but research independently published in 2018 suggests their range as of 2016 might be as far west as Oklahoma and north into Canada.
This potential range is the result of migrations during mating season (April through May) and doesn’t necessarily account for their true range.
This is a tiny spider, with females measuring just under ½ inch and males just under ¼ inch. These venomous spiders may have the iconic black widow shape, but boast very different markings.
They have an orange-red hourglass under their abdomen that’s either bisected or incomplete, orange-red dots down the midline of their abdomen on the top, and both males and immature females have white stripes on the abdomen as well as the dots. The same orange-red appears on portions of the legs.
Southern Black Widow (Latrodectus mactans)
When you think of black widow spiders, this is the species you’re likely to picture. The females are just over ½ inch long and males are just under ¼ inch, much like their northern siblings. While these spiders are often pictured as black with a red hourglass on the underside of their abdomens, the coloration is slightly different for males.
Males are actually purple or grey with a lighter hourglass that may lean closer to orange. Juveniles range from grey to black and have white abdominal stripes and orange and yellow spotting. Note that some females also have a dab of red on top of the spinnerets.
They’re common throughout the southeastern states ranging as far west as Texas and as far north as Ohio. It also has a presence in Hawai’i.
Western Black Widow (Latrodectus hesperus)
The western widow was once thought to be a subspecies of the southern widow due to the females’ nearly identical appearance. Not only do they share the same size, but the markings are also nearly identical.
Western widows may be brown to black and their hourglass is usually red to orange (although instances of yellow or even white have been observed in both species). They also have perhaps the largest range of the three, stretching through much of North America, although it tends to stay west of the Mississippi.
Distinguishing between the three species of US-based black widow can be frustrating and even scientists once confused all three. Northern widows have a similar appearance to juvenile southern widows, whose adult form closely resembles that of the western widow. However, scientists have since determined they are, indeed, three separate species.
Unlike most web-weaving spiders, the webs of these three widows are irregular and messy. They’ll usually hang out on the underside of their web. Females can also relay pheromone messages to potential mates through the silk.
All three species are known to lay a papery brown egg sac with up to 200 eggs. Once hatched, the mother continues to care for the white spiderlings until they’re able to fend for themselves, usually around a month later.
The average lifespan for black widows is one to three years in the wild, with males having a much shorter lifespan than their female counterparts.
What Do Black Widows Eat?
Black widows primarily eat insects and small arthropods, but will also consume smaller spiders. This has led to adaptations in female widow behavior. For example, the mother will carefully manage her eggs to ensure they all hatch around the same time. This is because she knows hatchlings will eat any siblings that are smaller in size.
See Also: Do Spiders Eat Roaches?
Are Black Widows Aggressive?
Where Do Black Widows Live?
These gals like their privacy and will gravitate towards undisturbed locations. They prefer old tree stumps, hollow logs, under firewood piles or brush, abandoned animal burrows, and even undisturbed leaf piles. When near humans, they aim for the corners of sheds, crawl spaces, basements, and attics.
They’re sometimes known to make their homes in the cracks of stone walls as well. Also, don’t be surprised if one or two migrate inside during the winter in search of warmth. It’s not uncommon for them to slip in through an open door or window. However, unlike wolf spiders, they’d rather find a quieter place to set up camp.
I Found a Black Widow Spider: Are There More?
Black widows are generally solitary spiders, only getting together to mate. However, if it’s mating season and a female has laid her egg sac, you could have quite a few spiderlings running around by summer.
Signs of an Infestation
The most obvious sign of a black widow infestation are the messy spider webs, although there are other species that can make similar webs. If you’re able to get a close look, you can check for the hourglass. Try using a camera’s zoom function so you don’t risk startling the spider.
What To Do When You Find a Black Widow
The first thing you should do is make sure your children or pets can’t get to it. A lot of people suggest destroying the web, but this isn’t always a good idea. The frightened spider will end up going into hiding or (even worse) try to bite you out of self-defense.
Remember, black widows aren’t aggressive and females rarely leave their web. Take your time and deal with the spider in a safe and responsible manner.
Black Widow vs Brown Recluse: Which is Worse?
There’s a big debate over whether black widows or brown recluse (Loxosceles reclusa) spiders are more dangerous. Both spiders are common in homes, and both are relatively harmless to adults while being more dangerous to children and pets.
In reality, the biggest threat from brown recluse spiders is necrosis while suffocation is the biggest risk (albeit even more rare) with black widow bites.
Black Widow vs Brown Widow
Black widows in the US are having some issues with sibling rivalry. The brown widow (Latrodectus geometricus) is less venomous than black widows but is slowly taking over black widow territory.
Believed to have originated from South America, these cosmopolitan spiders look a lot like black widows in shape but are smaller with different markings. They can range from black to tan or gray and have a bright orange to yellow hourglass instead of red.
They also feature striped legs. Their species name comes from the geometric black and white markings on their abdomen.
Black Widow vs False Widow
Also commonly known as the cupboard spider, the false black widow (Steatoda grossa) looks a lot like the black widow. It tends to be brownish-purple to black in coloration with males having slightly more reddish legs.
Unlike many widow species, the cupboard spider lacks an hourglass marking. It has the same messy webs and while less venomous than a black widow, their bite can still produce similar (albeit slightly less intense) symptoms.
Interestingly, this species will actively hunt black widows and is just one of many natural predators to the widows.
Black Widow vs Red Widow
The red widow (Latrodectus bishopi) is another native widow, this time from Florida. It has the usual widow body shape but is mostly red, with a black abdomen that has red spots ringed in yellow and one to two red spots instead of the famous hourglass.
They’re every bit as venomous as other widows but no bites have ever been recorded. Also, unlike black widows, these spiders prefer to live among sand pines which grow only in Florida. As of December 2022, they’re currently listed as vulnerable but stable and not considered dangerous.
How to Get Rid of Black Widows
Getting rid of black widow spiders is surprisingly easy, although you have to practice some caution in the process. Here are some of the most effective methods, as well as one method that doesn’t work so well.
When to Hire Professionals
Let’s start by bringing up the most costly approach and whether it’s even necessary. If you’ve only got one spider, you can probably handle it yourself. Remember, these are solitary spiders.
However, if it’s mating season, you might be dealing with a female spider and her egg sac. Thus you could be facing an eventual infestation if the spiderlings don’t balloon back outside.
Likewise, if you have pets or small children, the cost of an exterminator could well be worth it to not only eliminate the black widow but also to inspect your home for other issues.
The Hands-On Approach
While not recommended as a general rule, you can attempt to swat a black widow. This works the same as with any other spider (or fly), although you may wish to wear some thick gloves when killing them in this manner.
Of course, if you fail to kill the spider, she might attack out of fear, so this isn’t a method we’d recommend.
A much safer method is to use your vacuum cleaner to suck up the web, spider, and any potential egg sac, then dispose of the canister or bag safely.
Pesticidal sprays are going to produce very mixed results, depending on when you use them and which one you choose. Water-based sprays formulated for spiders can be quite effective against an adult, but is totally ineffective against her egg sac.
Instead, you will need a petroleum-based spray to bypass the protective coating of the egg sac and affect the eggs and hatchlings inside. This same rule applies to using spider bombs or foggers.
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Spider traps just aren’t that effective against female black widows as they rarely leave their webs. Instead, consider placing sticky traps nearby to capture any potential food.
This will generally convince the spider to move elsewhere. However, if you have a particularly high luck stat, the spider might wander onto one of the traps on her own.
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Diatomaceous Earth (DE)
Here’s something rather sneaky that can work wonders. Simply sprinkle a little food-grade diatomaceous earth onto the webs, being careful not to scare the spider. The gentle impact vibrations might fool the spider into thinking the DE is an insect.
Even if that’s not the case, the spider will eventually walk over the DE, which will lacerate her exoskeleton and cause her to die of dehydration.
Note that some people suggest using boric acid (or borax) for this same trick. Unfortunately, boric acid works best when ingested, which is something the spider isn’t likely to do.
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For a spider with such a dangerous reputation, black widows sure do have a lot of enemies. Wasps (including parasitic wasps), centipedes, mantises, scorpions, predator flies, birds, lizards, and even rodents will all munch on widows if they’re able to sneak up behind one.
Close the Buffet
It may sound silly, but sometimes the easiest way to get rid of back widows is to simply deal with the issues that attracted them in the first place. Black widows will seek warmth in the winter, but they often do this outside. Instead, seeing one indoors is almost always a sign that they were following potential food sources.
Check your home for any bug infestations and deal with them. Black widows are known to help control the populations of several insects, including harvester and fire ants. Additionally, they will go after small fliers such as cluster flies.
They’ve even been known to catch pests as big as mice in their webs. Getting rid of their food will generally convince a widow to move on without any further efforts.
Black Widow Prevention
The best problems to have are the ones you never had in the first place. Thankfully, there are some pretty easy ways to prevent black widows from taking up residence on your property or in your home.
It’s a simple fact that keeping your home and yard clean will reduce the risk of infestations, which could in turn attract black widows. You should also keep any wood piles tidy and away from the home.
Spiders don’t like stepping on strong scents (they smell through their feet), and essential oils also repel their prey. Try spraying some eucalyptus, lavender, lemon, peppermint, or tea tree oil where spiders or their prey are likely to visit.
This is an excellent way to leave a potential spider infestation out in the cold. Check your exterior walls for cracks and crevasses and seal openings as you find them. Make sure your window screens are in good shape and there are no gaps in door and window frames.
While it won’t stop ballooning baby spiders, you can lay a dead zone around your foundation at last six inches wide where there’s no vegetation. You can then use a barrier pesticide or insecticide dust to get anything that tries to cross the zone.
Black Widow Spider Disease and Venom Risks
Finally, let’s look at just how dangerous black widow spiders are and what to do if one bites you.
Are Black Widows Deadly?
The venom of a female black widow is 15 times stronger than that of a rattlesnake. Thankfully, these venomous bites are rarely fatal due to their small size. Despite this, black widows are a good example of why arachnophobia is one of the most common phobias out there.
A widow bite is far more dangerous to cats, dogs, and small children than a healthy adult. In fact, less than 1% of humans die from a widow bite, and the majority of those are children. Male black widows are generally considered harmless.
Bites by any member of the widow family result in a condition known as latrodectism. Pain is felt within moments of being bitten and grows worse over the next one to three hours and can last up to 24 hours.
The venom targets a victim’s central nervous system, potentially causing fever, increased blood pressure, muscle stiffness or spasms, nausea, sweating, and/or vomiting. The severity of the reaction depends largely on the amount of venom injected, location of the bite, and the health and size of the victim.
How To Treat a Black Widow Spider Bite
According to the Mayo Clinic, as soon as you’re bitten by a black widow, you should wash the area and apply an ice pack to slow the effects.
Once that’s done, consult with a doctor immediately, preferably with a photo of the spider itself to confirm its identity. The bites may have a low risk, but you never know when complications can occur.
Note that there’s no antivenom for northern black widows specifically, although a general Latrodectus antivenom can be used for all three species. Hospital stays may be necessary for the elderly, children, or pets.
Death is rare and almost always a result of suffocation due to paralysis of the diaphragm.