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Black Widow Spider Identification

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A close-up photograph of a female black widow. Note the robust body, long black legs, and red hourglass.

A close-up photograph of a female black widow. Note the robust body, long black legs, and red hourglass.

Black widow spiders, scientific name Latrodectus mactans, are among the most venomous of all arachnids. They are also among the most poisonous species in North America, and their bite can be fatal in some cases. If you found a spider and you suspect it may be a black widow, this article will help you identify your specimen. Black widows are relatively rare, and most of us will never see one, but if you do see one, you'll want to know exactly what you're dealing with!

I have been working with insects and spiders for almost 20 years, and I get a lot of questions about black widow spiders. What do black widows look like? Where do black widows live? Is the bite of the black widow spider fatal? These are all excellent questions. In this article I hope to answer at least some of your questions about these much-feared poisonous spiders. If you ever wondered what it's like to get bitten by a black widow, or the safest way to pick one up (it's not with your fingers), then this article will address your concerns.

Questions This Article Answers

  1. What do black widows look like?
  2. Where do black widow spiders live?
  3. What makes it a spider?
  4. What are the different body parts of a spider?
  5. How are male black widows different from females?
  6. Do black widows spin webs?
  7. Why do these spiders have fangs?
  8. How common are black widow bites?
  9. What's it like to be bitten by a black widow?
  10. What are the symptoms of a black widow bite?
  11. What's in the black widow's venom?
  12. How do you get rid of black widows?

1. What Do Black Widows Look Like?

Black widows are large spiders that spin tangled webs in sheltered places, both in nature and in your house. The distinctive sign of the black widow is a bright red hourglass marking on the animal's ventral side (the "bottom" or underneath). It's your surest guide to black widow identification—no other spider has it. In the natural world, bright red, orange, or yellow markings are universally used to signify protection by venom or caustic chemicals in the insect's haemolymph, or blood. This, in effect, tells everyone to "stay away from me, or you'll be sorry." But the classic hourglass shape is only one morph that spiders in the black widow's genus display. There are a couple of other variations that still serve the purpose of warning away predators.

If you ever get this close to a black widow, you'll see the true beauty of the species.

2. Where Do Black Widow Spiders Live?

Black widows typically live in your garage or your basement. They prefer dark, sheltered corners where they can spin their tangled webs and wait for the moths and other insects that make up their diet. Black widows do not want you messing with them. In fact, they view any interaction with you as a threat to their very existence. This is why the spiders will bite you—it's the only means of self-defense that they have.

Black widows live where you typically don't go, so you'll only encounter them when you're cleaning out a garage, or reaching into a dark corner of a basement. So be careful! If you make sure you can see where you're putting your hand, then the chances are pretty slim that a black widow will get her fangs into your flesh.

3. Black Widow Biology: What Makes It a Spider?

Black Widow identification begins with a question: What defines a spider? Spiders are a kind of arthropod, a huge group of animals that includes water-dwelling organisms like crabs and shrimp as well as all insects, including butterflies and moths. Spiders form a subset called "arachnids." They are separated from other closely related insects by several features: spiders have eight legs instead of six, two body sections instead of three, most spin webs with a special organ called a "spinneret" located at the tip of the abdomen, and all spiders are venomous. The venom of most spiders is only effective against the small invertebrates that they feed on, but a few have poison that can hurt vertebrates like humans. The black widow is one of a very few spiders with venom capable of seriously hurting humans.

4. What Are the Different Parts of the Spider?

PartDescription

1. Fang (chelicera)

The spider's fangs are sharp and deadly.

2. Venom gland

The glands connect to the fangs for quick delivery.

3. Brain

The spider brain must connect to many eyes and thus has a quite different structure to our own.

4. Pumping stomach

The stomach breaks down the food into a digestible soup.

5. Forward aorta branch

Like many other species, spiders have an open circulatory system.

6. Digestive cecum

The cecum or caecum is an intraperitoneal pouch that is considered to be the beginning of the digestive process.

7. Heart

They do not have true blood, or veins to convey it. Rather, their bodies are filled with haemolymph, which is pumped through arteries by a heart into spaces called sinuses.

8. Midgut

Glands that cause necrosis in the spider's victims.

9. Malphigian tubules

The Malpighian tubule system is a type of excretory and osmoregulatory system.

10. Cloacal chamber

The posterior orifice that serves as the only opening for the digestive, reproductive, and urinary tracts.

11. Rear aorta

Supplies haemolymph to the cephalothorax.

12. Spinneret

A spinneret is a silk-spinning organ of a spider or the larva of an insect.

13. Silk gland

The silk gland is used to create the spider's web.

14. Trachea

The trachea brings air into the spider's lungs.

15. Ovary (female)

Where the spider's eggs are produced.

16. Book lung

A book lung is a type of respiration organ used for atmospheric gas exchange.

17. Nerve cord

The nerve cord send sensory information throughout the body.

18. Legs

Spiders have eight, sharp legs that give them incredible balance.

19. Pedipalp

Appendages anterior to the first pair of walking legs.

5. How Are Male Black Widows Different?

The male black widow, as with many other spiders, is much smaller and less conspicuous than the female. His only real reason to exist is to impregnate the female, and once that's accomplished he becomes just another meal. While this may seem cruel—and is the source of the black widow's common name—it is actually a perfectly rational survival mechanism developed through millions of years of evolution. After all, when food is survival, and the male is no longer needed, the solution is obvious.

Being a male black widow is a tough job. To identify a male, look for the light brown brown body and its disproportionately large eyes.

Being a male black widow is a tough job. To identify a male, look for the light brown brown body and its disproportionately large eyes.

6. Do Black Widows Spin Webs?

The black widow spins a characteristic tangled web in a dark corner. She waits for insects to come along and wander into the web, upon which she grabs her prey, bites it, and sucks the digested insides of the insect out with her hollow fangs. The web is one way to identify black widows, but lots of other spiders spin similar webs, so don't jump to conclusions. Wait to actually see the red hourglass on the shiny black underside of the spider to determine if it is actually a black widow spider.

A black widow building a web.

A black widow building a web.

Female black widow with her prey.

Female black widow with her prey.

Some spiders are capable of subduing even those insects with poison defenses of their own. This large female has captured not one but two wasps capable of inflicting a powerful sting to any predator, but the spider has avoided the stinger and inflicted its own fatal bite. Soon these wasps will be a meal for the spider.

Her venom paralyzes, then liquifies, the insect, and the spider wraps the meal in silk to further control and preserve it. This spider has killed a small insect, and is siphoning out the liquified insides with its straw-like fangs.

A black widow's egg sac.

A black widow's egg sac.

7. Why Do These Spiders Have Fangs?

The fangs of the Black Widow, and all spiders, are believed by some researchers to be a highly evolved pair of legs that long ago became adapted to subduing prey. They are essentially hollow tubes that act like hypodermic needles to inject poison. The poison needs to be powerful and fast acting, since the less the prey struggles in the web, the less damage the spider will have to repair. The toxin also often acts as a liquifying agent, turning the prey's insides into a kind of soup that the spider then sucks up through the same fangs that were used to inject the venom.

Black Widow Eating

Black Widow Eating

8. How Common Are Black Widow Bites?

Black Widow bites are rare, since the animal spends most of its time in its web, unlike the Brown Recluse, which roams at night in search of prey and could wind up under your sheets (a truly unpleasant thought). To be bitten by the Black Widow, you basically need to come to the spider, since it probably won't come to you. This means putting your hand in a dark corner of the basement or garage (or even in a tree stump).

I once found an enormous female who had built a nest in a dead tree, about head level. Once bitten, your prognosis is not good. Fatalities are rare, but you are likely in for several days of the effects of the spider's neurotoxic venom.

black-widow-identification

9. What Is It Like to Be Bitten by a Black Widow?

Black widows leave two little marks... That's usually all you can see from a black widow bite. The fangs just puncture the surface, but it's enough to deliver the venom.

First-Person Account of Black Widow Envenomation

I've been bitten by a black widow spider. I grabbed a pair of old shoes from the garage, and hastily threw them on over my bare feet, and continued my charge around the house to build momentum to get out the door. About a minute later, I realized that there was some wiggling in the toes in my right shoe, and just as I was about to take my shoe off, I felt a bite on my 2nd toe (it wasn't painful, just a bit annoying). Later, the pain was excruciating.

The medical literature suggests that recovery happens within three to five days. Nights three, four, and five were complete disasters for me. For some completely unknown reason, I was sweating profusely at night. As in, literally soaking through my sheets and changing my sheets three times one night and twice the next. The pain is not just related to body temperature, the experience can vary. Below you'll find the full symptoms of a black widow bite.

10. Symptoms of a Black Widow Bite

Symptom Description

Local pain

The point of contact feels a burning sensation and can become necrotic.

Muscle cramps

Muscle contract rapidly, causing cramping.

Abdominal pain

This muscle cramping extends to the abdomen causing further pain.

Weakness and tremor

The neurotoxin causes shaking and weakened muscles.

Nausea and vomiting

The neurotoxin causes the digestive system to go haywire, causing vomiting as the body tries to rid itself of the toxin.

Fainting

The pain, nausea, and fatigue can lead to fainting.

Chest pain

As your heart beats faster and faster, your chest begins to hurt. Some people even have heart-attacks.

Respiratory difficulties

As the muscles throughout your body shut down, your lungs are no exception. It will become harder and harder to breathe as your heart goes into a panic.

11. What's In the Black Widow's Venom?

Black Widow venom is complex, and contains a number of compounds that further the evolutionary goal of subduing prey and protecting the animal from predators. The most specific ingredients to the genus Latrodectus are a number of toxins called, appropriately, latrotoxins. Latrotoxins are very large molecules with dozens of different atoms, and the way they work is still not well understood. Black Widow venom contains at least seven different latrotoxins (most of which specifically effect invertebrates, or insects, which form the bulk of the spider's diet). There is one, however, called alpha-latrotoxin, which targets vertebrates—including humans. This powerful poison is specific to the genus Latrodectus and is the reason the spider is so toxic to humans.

Tools for Getting Rid of Black Widows

ToolAverage Price

Bug Vacuum

$13

Window Sealant

$6

Zenprox Aerosol

$20

Stryker 54 Contact Spray

$30

12. How to Get Rid of Black Widows

It can be difficult to manage black widows in your home, especially since they are so good at hiding. However, if you take certain precautions, you will be far less likely to get bitten.

Ways to Avoid Black Widow Bites

  • Keep beds away from the walls.
  • Don't store boxes or any items under your bed.
  • Keep dust ruffles or bed skirts from touching the floor.
  • Don't store shoes on the floor or any clothes, towels or other linens (always shake out shoes and clothes before using).
  • Store sports equipment like rollerskates, gardening clothes, gloves, ski boots in plastic bags that are tightly sealed with no holes.
  • Vacuum under furniture, closets, under heaters, around all baseboards and other areas of the house to eliminate habitat.
  • Keep screens on windows and fix or replace screens with holes or that don't fit snuggly.
  • Seal doors with weather stripping and door sweeps.
  • Seal cracks, access holes for electrical conduits or plumbing.
  • Remove spider webs and egg sags when found.

Other Bugs That Get Into Your House

InsectDescription

Centipedes

Arthropods belonging to the class Chilopoda of the subphylum Myriapoda, an arthropod group which also includes Millipedes and other multi-legged creatures.

Silverfish

A silverfish is a small, wingless insect.

Ants

Social insects of the family Formicidae and, along with the related wasps and bees, belong to the order Hymenoptera. Ants evolved from wasp-like ancestors in the Cretaceous period.

black-widow-identification

Seen Any Black Widows Lately? Leave a Comment!

Heidi on May 25, 2020:

I spotted a black widow a few years ago in Arizona and haven't been able to find any pictures or info on it. It looked like a normal black female with a red time glass on her belly but had thin white lines on her back.

bill nelson on March 15, 2019:

Very useful information. I recently purchased a new car in California in February. Last week, I went into my garage and saw a large Black widow spinning a web from my front left bumper to the floor. I immediately squashed it. Then tonight, I was cleaning my new car and spotted another one on the right side of the car. I looked down and saw smaller one on the floor near some items. Now I'm concerned that the Black widow could have stowed away on the new car and are coming out. I've only seen and killed one Black widow in my garage in 10 yrs. Any advice will help. Thank you.

Brendan Asmussen on June 16, 2018:

Well it's all quite amusing really to think that the spider and her crew can actually eat the Male,there is cases we have studied the in a odd ocasion the Male will turn and the hunter becomes the hunted.Just a little food for thought yummy

Scott S Bateman on November 16, 2015:

The headline for this article caught my attention because I have heard several times that black widows have been spotted in my neighborhood.

I haven't found one yet, but I'm concerned because I spend a lot of time in our basement and backyard.

Your article will make me more observant going forward. I also have to say that it is exceptionally thorough, visual and informative. Nicely done.

RANADEEP on August 14, 2013:

I think it is scary though,but it will not bite unless it feels insecure!!A very good lense in this topic!!

Barbara Radisavljevic from Templeton, CA on July 13, 2013:

I followed an image I thought might be an American House spider here from Google, and it turned out to be your male black widow. I'm quite sure it's not the one hanging over my shower and in the corners of the ceilings all over the house. I believe they are umbrella spiders, but I can't find this as a scientific or even common name when I search for them online. Anyway, that's how I wound up here. Excellent lens.

anonymous on July 08, 2013:

I saw one in my home last week and I'm terrified, I hate spiders or any kind of bugs, and I'm super scared right now

The spider is in this spot of my house that I can't reach, what can I do?

anonymous on November 27, 2012:

Oh, these are scary insects, glad we don't have any around, well...except for some people's pets. :)

anonymous on October 01, 2012:

Found one in my baggie of grapes this morning.....that was a delightful start to my Monday morning!!!

sherioz on August 28, 2012:

Luckily I've never met a dangerous spider in person. These are gorgeous spiders and I hope I never see them off the printed page or computer screen. Blessed.

anonymous on August 18, 2012:

I live in Marietta Ga and my back yard seems to be infested with black widows. We saw 2 yesterday. We had a dumpster of dirt delivered about a month age and my kids played in it till it became some compacted. As we were picking up small rocks for an art project my son flipped over a med size rock and there it was. I tried to kill it with a shoe, but when I missed it began running and got away. He then flipped over a small rock and there was another one, Now my back yard is considered a danger zone. Should I put sticky pads all over the yard or is there a spray/power or something that will make them get, go or die. I know they are good for bug control, but I have babies walking around my back yard.- HELP!! fyi-normal, I'm not scared of them because they are not aggressive, its the quantity that concerns me.

KandDMarketing on July 26, 2012:

Black Widows and Brown Recluse are both relatively common in and around the Ozarks region of southern Missouri and Northern Arkansas. You just need to be aware of them.

tfsherman lm on July 20, 2012:

Gorgeous web! I'm very fond of spiders -- not black widows though.

UKGhostwriter on June 04, 2012:

Never seen a live one ..even a tiny money spider can cause havoc in my family

gottaloveit2 on April 19, 2012:

I hate spiders, period! And, with a house that's 160 years old, I can't get away from them. Spider spray is my best friend.

June Campbell from North Vancouver, BC, Canada on April 17, 2012:

I have never seen one. I am happy to leave it that way.

JoshK47 on April 14, 2012:

Positively wonderfully presented information here - thankfully, I've not seen any around here! Blessed by a SquidAngel!

KathyBatesel on April 13, 2012:

As a kid, I used to go on weekly widow hunts with Raid. My house literally had dozens of them around our hose faucets, in my father's workbench areas and our storage unit every time I did! As I got older and didn't play outside as much, I stopped. In high school, I awoke with a weird little pimple-like nodule on my thigh. I popped it, but by my second class of the day it had gotten huge - larger than a coffee cup saucer and HOT to touch. The school nurse said it was probably a black widow bite, which aren't all that rare in Arizona. When I got home, I went to find where it might have come from inside my house, and I discovered several webs and adolescent spiders on the sides of our sofa. I believe that was an adolescent bite, though some sources say the young are harmless.

Some years later, I was sitting on a pipe ell at my school and was bit on the foot. This time, I saw the spider. Again, lots of swelling and hot to the touch, but those are the only symptoms I got either time.

laughingapple on April 11, 2012:

Excellent lens. I have run into these spiders a few times in the wild. They look beautiful but of course are best appreciated from afar(or in photos).

anonymous on April 11, 2012:

I haven't and hope to keep it that way. What an amazingly informative lens. Well done.

Ellen Gregory from Connecticut, USA on April 11, 2012:

I saw one about 7 years ago crawling on the side of my house near the bulk head door. I killed it. I was afraid it might multiply and get into my crawl space.

iWriteaLot on April 11, 2012:

What a creepy lens! But very informative. To think that a bit that tiny could do so much damage. But it's good to know that they only bite if you go after them. *shivers*! Blessed.... at a distance! LOL

Joan Haines on March 30, 2012:

"Squid Angel blessed."

Joan Haines on March 30, 2012:

When I was nine, our house was overrun with black widows. True story.

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