Black Widow vs False Widow
Verdict: Check for red. A shiny jet black spider with a red mark under the abdomen is a black widow, and a brown spider with no red belly is a false widow. Black widows are the dangerous ones.
Black widows and false widows are close relatives with round, bulbous abdomens, and both hang upside down in a messy web. A mature female black widow is shiny black, about 1/2 inch long, with a red hourglass or similar red pattern underneath. The false widow is chocolate or dark brown and never has red on its belly.
The hourglass can vary, sometimes split into two triangles, orange, or faint, so use color and size together. False widows are slightly smaller at about 1/5 to 3/8 inch and often live indoors, while black widows prefer outdoor spots near buildings. A false widow bite is mild, but a black widow bite can cause serious symptoms.
Black Widow vs False Widow side by side
| Trait | Black Widow | False Widow |
|---|---|---|
| Color | Shiny jet black | Chocolate to dark brown, with lighter markings |
| Red marking | Red hourglass or pattern under the abdomen (can be orange or white) | Never red on the belly; no hourglass |
| Female size | About 1/2 in body length | About 1/5 to 3/8 in |
| Abdomen markings | Solid black apart from the red mark | Dark brown with variable lighter markings |
| Web | Irregular, tangled cobweb | Irregular cobweb |
| Web location | Outdoors near structures, in sheds and woodpiles | Often indoors, bathrooms and under furniture, or at ground level near rocks and logs |
| Bite effect | Pain, spreading muscle cramps, nausea, sweating, high blood pressure | Mild burning and swelling, like a wasp sting |
| Medical risk | Antivenom exists, but is reserved for severe cases | Medical care usually not needed |
| Relationship | Same family as false widows | Close relative in the same family as black widows |
Last verified October 2026. Typical values; individual animals, products and local prices vary.
When you are looking at which
Black Widow
- A shiny jet black spider hanging upside down with a red mark on the underside.
- A black spider outdoors around a building or its outbuildings.
- A rounded body about half an inch long, shiny from end to end.
- A disorganized, tangled web with the spider hanging in it.
False Widow
- A brown or chocolate spider with no red anywhere on the belly.
- A dark brown spider in a bathroom, closet or under furniture indoors.
- A slightly smaller spider, about 1/5 to 3/8 inch, with lighter markings on the abdomen.
- A spider that built its cobweb near ground level, around rocks, logs or boards.
How this works
The quiz scores color, red marking, size, location and shine. Color and red marking carry the most weight, so answer those first if you can see them from a distance. Color and the red mark get the most weight because they separate the two most clearly in a photo.
Several other spiders are called false widows, and some widow patterns are faint or hidden. When in doubt, treat the spider as a black widow, avoid handling it and photograph it for an expert. Never move a spider to check its belly. Use a flashlight and photograph it from a distance, then ask a pest professional or extension office.
Where these numbers come from
The figures and defaults on this page are based on:
- UC IPM: Widow Spiders and Their Relatives, Size, color, red marking, webs, habitat and bite effects (checked October 2026)
- Montana State University Extension: False Widow, False widow size, color, web location and relationship to black widow (checked October 2026)
- Poison Control: Black Widow Spiders, Black widow identification, bite symptoms and when to call (checked October 2026)
Field-identification guide, not medical advice. Seek medical care or call Poison Control for any suspected widow bite.
Frequently asked questions
What are the symptoms of a black widow bite?
Pain starts right away, with muscle cramps that spread outward in 15 to 60 minutes, nausea, sweating and high blood pressure. Most people recover in 24 to 48 hours.
Are false widows dangerous?
Generally not. The bite is mild, with local burning and swelling like a wasp sting, and medical care is usually unnecessary.
Do all black widows have a red hourglass?
No. The red mark varies. It can be split into two triangles, be orange, white or tan, or be very small or missing.
Do black widows live indoors?
They prefer outdoor spots around buildings and rarely survive inside homes because of limited prey. False widows are the usual indoor spider.
Explore the whole Calcs family here.
Not happy with the answer or how it works? Let us know.
Have a suggestion for a comparison you don't see here? Let us know.
All VersusCalcs tools
Animals
American Crow vs Raven Anaconda vs Python Antelope vs Deer Ape vs Monkey Badger vs Wolverine Bald Eagle vs Golden Eagle Beagle vs Basset Hound Bernese Mountain Dog vs Saint Bernard Bison vs Yak Black Bear vs Grizzly Black Widow vs False Widow Bobcat vs Lynx Border Collie vs Australian Shepherd Boxer vs Bulldog Buffalo vs American Bison Butterfly vs Moth Camel vs Dromedary Carpenter Bee vs Bumble Bee Cavalier vs Cocker Spaniel Centipede vs Millipede Cheetah vs Jaguar Chihuahua vs Pomeranian Chimpanzee vs Gorilla Cicada vs Locust Copperhead vs Corn Snake Copperhead vs Water Snake Corgi vs Shiba Inu Cottonmouth vs Water Snake Coyote vs Fox Crocodile vs Alligator Crow vs Blackbird Deer vs Elk Doberman vs Rottweiler Dolphin vs Porpoise Donkey vs Mule Dragonfly vs Damselfly Duck vs Goose Eagle vs Hawk Elk vs Moose Flea vs Tick Fox vs Wolf Frog vs Toad Garter Snake vs Ribbon Snake Goat vs Sheep Goose vs Swan Gorilla vs Orangutan Grasshopper vs Locust Great Dane vs Mastiff Grizzly vs Brown Bear Groundhog vs Woodchuck Hamster vs Gerbil Hare vs Jackrabbit Hawk vs Falcon Heron vs Crane Heron vs Egret Honey Bee vs Bumble Bee Hornet vs Wasp Hornet vs Yellow Jacket Husky vs Malamute Iguana vs Lizard Jackal vs Hyena King Snake vs Coral Snake Labrador vs German Shepherd Leopard vs Jaguar Lion vs Leopard Lion vs Tiger Lizard vs Salamander Llama vs Alpaca Maltese vs Bichon Frise Manatee vs Dugong Mink vs Otter Monkey vs Lemur Mosquito vs Gnat Mouse vs Rat Orca vs Killer Whale Osprey vs Eagle Otter vs Beaver Owl vs Hawk Paper Wasp vs Mud Dauber Pigeon vs Dove Pitbull vs Rottweiler Poodle vs Labradoodle Praying Mantis vs Stick Bug Python vs Boa Rabbit vs Hare Reindeer vs Caribou Salamander vs Newt Shark vs Dolphin Spider vs Scorpion Squirrel vs Chipmunk Starling vs Blackbird Stingray vs Skate Stork vs Crane Tick vs Bed Bug Tiger vs Jaguar Tortoise vs Terrapin Turtle vs Tortoise Vole vs Mouse Vulture vs Buzzard Walrus vs Seal Wasp vs Bumble Bee Water Buffalo vs Bison Weasel vs Ferret Wolf vs Coyote Yellow Jacket vs WaspAuto & Tools
5W30 vs 5W20 AWD vs 4WD All-Season vs All-Weather Tires Brushless vs Brushed Drill EV vs Hybrid Gas vs Diesel Pickup Truck Impact Driver vs Impact Drill Premium vs Regular Gas TIG vs MIG WeldingHome
Brass vs Bronze Concrete vs Asphalt Driveway Cotton vs Polyester Gas vs Electric Dryer Granite vs Marble Hardwood Floors vs Carpet Hardwood vs Engineered Flooring Linen vs Cotton Mini-Split vs Central Air Nylon vs Polyester Oak vs Maple PVC vs CPVC Pine vs Cedar Portable vs Window Air Conditioner Quartz vs Granite Countertops Shingles Roof vs Metal Roof Silk vs Satin Spray Foam vs Fiberglass Insulation Stainless Steel vs Aluminum Tank vs Tankless Water Heater Vinyl vs Laminate Flooring Wool vs CashmereKitchen
Air Fryer vs Convection Oven Blender vs Food Processor Cast Iron vs Stainless Steel Catfish vs Bullhead Clam vs Oyster Gas vs Electric Stove Instant Pot vs Crock Pot Lobster vs Crawfish Octopus vs Squid Salmon vs Trout Shrimp vs Prawn Toaster Oven vs ToasterYard, Pool & Garden
Cedar vs Juniper Centipede Grass vs St Augustine Chlorine Pool vs Salt Water Composite vs Wood Decking Crabgrass vs Nutsedge Determinate vs Indeterminate Tomatoes Maple vs Sycamore Mulch vs Rock Landscaping Pellet Grill vs Gas Grill Perennial vs Annual Pine vs Spruce Riding Mower vs Zero Turn Sod vs Seed Spruce vs Fir St Augustine vs Bermuda GrassTime Zones
AKST vs AKDT AKST vs PST BST vs GMT CST vs CDT CST vs MST CST vs PST Central vs Mountain Time Central vs Pacific Time EST vs CST EST vs EDT EST vs MST EST vs PST Eastern vs Central Time Eastern vs Mountain Time Eastern vs Pacific Time HST vs PST MST vs MDT MST vs PST Mountain vs Pacific Time PST vs PDT UTC vs GMTLanguage
Affect vs EffectNo tools match your search.