Yes, Wisconsin has black widows. There is a single native species, and it has been here all along rather than arriving recently. It is rare enough that most residents will never see one, and the dark, shiny spider you found in the garage is far more likely to be a harmless look-alike.
Where Black Widows Live in Wisconsin
Wisconsin’s native widow is the northern black widow, one of several widow species in North America.1UW Insect Diagnostic Lab. Are There Black Widows in Wisconsin? It has been documented in fewer than 10 of the state’s 72 counties.2UW Insect Diagnostic Lab. Are There Black Widows in Wisconsin?
Most Wisconsin records come from east-central counties.3PBS Wisconsin. Northern Black Widow Is Rare In Wisconsin, But Sightings Spiked In 2017 Door County has the most confirmed sightings and is sometimes called the state’s black widow capital.4PBS Wisconsin. Northern Black Widow Is Rare In Wisconsin, But Sightings Spiked In 2017 Other confirmed reports tend to come from counties that also border Lake Michigan.5PBS Wisconsin. Northern Black Widow Is Rare In Wisconsin, But Sightings Spiked In 2017 Away from the lake, widows have been found in prairie areas in Sauk, Crawford and Grant counties.6PBS Wisconsin. Northern Black Widow Is Rare In Wisconsin, But Sightings Spiked In 2017 A spider found far from Lake Michigan or the southwestern prairies is more likely a look-alike, so a clear photo is a better first step than assuming the worst.
Widows are more at home in warmer places, and Wisconsin’s cold winters make it hard for them to establish themselves across most of the state. Sheltered spots such as rock piles, stone walls, and spaces under buildings protect a few spiders through winter, which helps explain why they persist in pockets.
On your own property, a widow would favor dry, undisturbed places: woodpiles, stone walls, rock piles, sheds and other outbuildings, and the undersides of outdoor furniture. They rarely live in the heated, busy rooms of a house.
Widows can also arrive from other states in grapes, luggage, or goods shipped from warmer places. Finding one that way doesn’t mean a local population exists.
How to Recognize a Northern Black Widow
Females of the northern black widow have a red hourglass on the underside that is broken into two separate parts.7Missouri Department of Conservation. Black Widow Spiders They usually have a row of red spots down the top of the abdomen, which can be faint or bold.8Missouri Department of Conservation. Black Widow Spiders Some also have diagonal whitish markings on the sides.9Missouri Department of Conservation. Black Widow Spiders
The southern black widow has a single connected hourglass instead.10Missouri Department of Conservation. Black Widow Spiders A fully joined hourglass on a Wisconsin spider may suggest one that traveled from the South, though hourglass markings vary and an expert should confirm the species.
Adult females have a round, shiny, pea-sized abdomen and long legs. Males and young spiders are smaller and paler, often patterned with lighter marks. Widows build a messy, tangled web low to the ground rather than a neat wheel, and they usually hang upside down in it, which shows the belly. Black color alone doesn’t make a widow, and red spots on top without a mark on the underside don’t confirm one either.
Never pick the spider up with bare hands, since a pinched widow is the one most likely to bite. Set a clear jar over it, slide a piece of paper underneath, and tip it gently to see the belly. A close phone photo lets you zoom in on the underside later without staying near the spider. A dead spider can be turned over with tweezers.
Spiders Commonly Mistaken for Black Widows
The false black widow is chocolate brown and never has red coloration.11UC Statewide IPM Program. Widow Spiders and Their Relatives / Home and Landscape / UC Statewide IPM Program (UC IPM) It has a similar body shape, and false widows are among the most common spiders mailed to experts by people who fear a dangerous species.12Journal of Medical Entomology. Arachnids Submitted as Suspected Brown Recluse Spiders (Araneae: Sicariidae): Loxosceles Spiders Are Virtually Restricted to Their Known Distributions but Are Perceived to Exist Throughout the United States13UC Statewide IPM Program. Widow Spiders and Their Relatives / Home and Landscape / UC Statewide IPM Program (UC IPM)
Other spiders often confused with widows include the common house spider, the bold jumper, and several orb weavers.14BuzzSkito. Black Widow Spider: ID, Range and Look-Alikes Bold jumpers are fuzzy, with pale spots on top of the abdomen, and they leap rather than hang in a web. Common house spiders are mottled brown and gray rather than glossy black. Orb weavers build round, wheel-shaped webs, unlike the tangle a widow makes. If you can’t tell15BuzzSkito. Black Widow Spider: ID, Range and Look-Alikes, treat it as a widow and avoid handling it.
For a confirmed identification, the UW Insect Diagnostic Lab accepts photos and specimens. Put a captured spider in a sealed container with rubbing alcohol, and note where and when you found it, sealing the lid before handling the container. A confirmed record also helps track the species in the state.
Does Wisconsin Have Brown Recluses Too
Wisconsin is outside the native range of the brown recluse.16PBS Wisconsin. Northern Black Widow Is Rare In Wisconsin, But Sightings Spiked In 2017 Recluse spiders are virtually restricted to their known range, even though people believe they live across the whole country.17Journal of Medical Entomology. Arachnids Submitted as Suspected Brown Recluse Spiders (Araneae: Sicariidae): Loxosceles Spiders Are Virtually Restricted to Their Known Distributions but Are Perceived to Exist Throughout the United States A brown spider found in Wisconsin is almost certainly something else.
Many skin sores are blamed on recluse bites even though no spider was ever seen, and infections or other medical conditions often explain them. A spreading or worsening sore should be seen by a doctor rather than assumed to be a spider bite.
How Often Black Widows Bite
When gently poked, widows mostly move away or pull back.18Animal Behaviour. Poke but don ’t pinch: risk assessment and venom metering in the western black widow spider, Latrodectus hesperus When pinched or squeezed, they are much more likely to bite.19Animal Behaviour. Poke but don ’t pinch: risk assessment and venom metering in the western black widow spider, Latrodectus hesperus
More than half of widow bites can be dry, with no venom delivered.20Animal Behaviour. Poke but don ’t pinch: risk assessment and venom metering in the western black widow spider, Latrodectus hesperus A widow also delivers nearly twice as much venom when squeezed on the body than on a leg.21Animal Behaviour. Poke but don ’t pinch: risk assessment and venom metering in the western black widow spider, Latrodectus hesperus Nationwide, bites happen most in warm states and in summer.22PubMed. Black Widow Spider Exposures: A Retrospective Review of the National Poison Data System 2012-2022
The usual setups are ordinary. Pulling on gloves or boots stored in a garage or shed can press a hidden spider against skin, as can reaching blindly into a woodpile or under a ledge. Shaking out stored items before use prevents most of these encounters.
A bite may feel like a pinprick or go almost unnoticed. Two tiny marks may be visible. Symptoms, if any, usually build within an hour.
What a Black Widow Bite Does and How It Is Treated
The venom makes nerve endings dump their chemical signals all at once.23PubMed Central. α-latrotoxin triggers transmitter release via direct insertion into the presynaptic plasma membrane Muscles can then cramp, and pain can spread well beyond the bite.
Pain at the bite site often comes first, and cramping can then spread to the large muscles of the back, abdomen, or thighs. In more significant cases, sweating, nausea, and restlessness can join the pain. Most symptoms peak within hours and then fade.
Across U.S. poison center reports, almost half of widow bites were managed outside a healthcare facility.24PubMed. Black Widow Spider Exposures: A Retrospective Review of the National Poison Data System 2012-2022 About 1 in 10 people needed hospital admission.25PubMed. Black Widow Spider Exposures: A Retrospective Review of the National Poison Data System 2012-2022 Wound care was the most common treatment, and about 1 in 5 received muscle-relaxing medicine.26PubMed. Black Widow Spider Exposures: A Retrospective Review of the National Poison Data System 2012-2022
Mild to moderate cases are mainly treated by easing symptoms, while severe cases may get pain medicine, muscle relaxants, or antivenom, a medicine made from antibodies that counteracts the venom.27PubMed Central. Treatments for Latrodectism—A Systematic Review on Their Clinical Effectiveness Antivenom was given in about 3 in 100 cases nationwide.28PubMed. Black Widow Spider Exposures: A Retrospective Review of the National Poison Data System 2012-2022 Doctors have worried about allergic reactions, though later studies suggest those risks were overstated.29PubMed Central. Treatments for Latrodectism—A Systematic Review on Their Clinical Effectiveness It is still debated whether antivenom helps enough to use routinely.30PubMed Central. Treatments for Latrodectism—A Systematic Review on Their Clinical Effectiveness In children treated with it, symptoms improved within minutes and all went home within hours.31PubMed. Treatment of pediatric black widow spider envenomation: A national poison center’s experience
After a suspected bite, wash the area with soap and water and apply a cold pack to ease pain. Call Poison Control at 1-800-222-1222 for guidance on what to do next. Bring the spider or a photo if that can be done safely. Seek emergency care for severe cramps, chest or belly pain, or trouble breathing.
Young children, older adults, and people with heart conditions should be seen promptly. Spreading belly rigidity can mimic appendicitis, so tell doctors about the bite. With care, symptoms usually ease within a day or a few days.
Keeping Widows Away From Your Home
Some tiny wasps and flies parasitize widow egg sacs.32Wikipedia. Latrodectus mactans – Wikipedia Certain wasps, such as the blue mud dauber, hunt adult widows.33Wikipedia. Latrodectus mactans – Wikipedia Avoiding broad pesticide spraying keeps these helpers around.
Beyond that, stack firewood off the ground and away from the house. Clear rubble, boards, and clutter from sheds and garages, and seal gaps around doors and foundations. Vacuum up webs and egg sacs and dispose of the bag.
Pest control is rarely needed given how rare widows are in Wisconsin. Repeated confirmed widows in one spot suggest a hidden nest area, and that is the time to call a professional. Confirm the identification first so you don’t treat for a harmless spider.