Northern Black Widow (Latrodectus variolus)
The northern black widow is the widow of the eastern woods — the species that reaches further into Canada than any other North American widow, and the one whose red hourglass is broken into two separate marks. It is shy, slow and almost never seen indoors, but its venom is medically significant and a bite is a genuine reason to be seen by a doctor.
By Dr Richard J. Pearce (PhD)Published April 23, 2019Updated September 13, 2026✓ Reviewed by Dr. James Watuwa
In this guide
- Physical description and identification
- Where the northern black widow lives
- Are northern black widow spiders venomous?
- Can northern black widow spiders bite?
- Ecological importance and behaviour of the northern black widow
- Similar spiders and how to tell them apart
- Quick facts
- Did you know?
- Frequently asked questions
Physical description and identification
Latrodectus variolus is built like every other widow: a small, low carapace, long thin legs and an abdomen that is almost spherical in a mature female. What sets it apart is the pattern. Where the southern black widow wears one connected red hourglass, the northern wears two separate red marks — and it usually carries a line of red spots along the top of the abdomen as well.
Adults
- Size: females measure about 9–11 mm in body length, with a leg span of 25–35 mm. Males are 4–5 mm, roughly half the female's length and a fraction of her weight.
- The split hourglass: on the underside of the female's abdomen the red hourglass is divided into two separate triangles or bars, with a gap of black between them. This is the single most reliable field character separating her from the southern black widow.
- Dorsal markings: females typically show a row of red spots running down the midline of the upper abdomen and a series of pale or white diagonal bands on each side. Some older females darken almost to plain black.
- Males and juveniles: males are not black. They are grey to tan or brown, with four pale diagonal bands along each side of the abdomen and small red spots. Juveniles of both sexes look like males and darken as they mature, so a brown, striped widow-shaped spider is almost always an immature or a male.
- Legs and comb: the legs are long, smooth and glossy, and the fourth pair carries the row of curved bristles — the comb — that all cobweb spiders use to throw silk over struggling prey.
Eggs and egg sacs
The female builds a pale grey to tan, papery, roughly spherical sac about 10–13 mm across and hangs it in the densest part of her web, where she guards it. A sac commonly holds a few hundred eggs — figures of roughly 100 to 400 are normal — and a female may produce several sacs across a summer, so the older claim of "up to 200 eggs" understates her output. Incubation takes about two to four weeks depending on temperature.
Spiderlings
Spiderlings emerge inside the sac, moult once and chew their way out within days to a couple of weeks. They do not stay for a month, and their mother does not feed them: crowded siblings turn cannibalistic quickly, so they disperse fast, many of them by ballooning on a thread of silk. Survivors reach maturity in two to four months in warm weather, or overwinter as juveniles further north.
The web
The web is an irregular, strong, three-dimensional tangle of coarse silk with taut gumfoot lines running down to an anchor point, each line beaded with glue at the base. Prey that touches one sticks, pulls the thread free and is swung off the ground. The northern black widow more often builds up in vegetation than its southern relative — in the low branches of shrubs and trees, in stumps, hollow logs, stone walls, fence lines and the corners of sheds and outhouses. It rests upside down at the hub, and with poor eyesight it reads everything through vibration, as explained in our guide to spider webs.
Where the northern black widow lives
This is an eastern North American species with the most northerly distribution of any widow on the continent. It ranges from northern Florida up the Atlantic seaboard to New England and into southern Canada, with records in Ontario, Quebec and the Maritimes, and west through the Appalachians and Great Lakes states to eastern Texas, Oklahoma and Kansas. In Michigan and other northern states it is the only widow present, and it is uncommon enough there to be a notable find.
It favours undisturbed, sunny, sheltered places with something to anchor a web to: old stumps, hollow logs, brush piles, rock and stone walls, the underside of fallen timber, the base of shrubs, and human structures such as sheds, barns, outhouses, woodpiles and unused garden equipment. Unlike the western black widow it rarely sets up inside occupied houses, which is one reason bites are uncommon across its range.
Are northern black widow spiders venomous?
Yes, and this one matters. Like all widow spiders, Latrodectus variolus produces venom containing alpha-latrotoxin, a neurotoxin that forces nerve endings to dump their neurotransmitters. The result in a person is latrodectism: pain and muscle cramping that spreads well beyond the bite site.
The often-repeated line that widow venom is "fifteen times stronger than a rattlesnake's" comes from drop-for-drop toxicity tests in mice and is misleading. A widow injects a few micrograms at most, while a rattlesnake delivers hundreds of milligrams, so the two cannot be compared as threats. The honest summary is that the venom is genuinely potent, the dose is tiny, serious illness is possible, and death is exceedingly rare — the "one per cent mortality" figure still quoted online comes from early twentieth-century case series and does not reflect modern outcomes.
Can northern black widow spiders bite?
They can, but they are timid. A widow's first responses to disturbance are to freeze, drop out of the web or curl into a ball. Almost all bites happen when the spider is pressed against skin — a hand into a woodpile, a foot into a boot left in a shed, or a body rolling onto a spider in bedding.
What a bite feels like: the initial pinprick is often barely noticed. Within about 30 minutes to two hours, pain builds at the site and spreads to the large muscle groups — cramping in the abdomen, back and thighs is the classic picture. Other features include sweating (sometimes localised to the bitten limb), raised blood pressure, a fast heartbeat, nausea, headache, restlessness and a target-like red mark. Symptoms usually peak within the first day and settle over one to three days, occasionally longer.
What to do if you are bitten: wash the area with soap and water, apply a cold pack, keep the limb still and get medical assessment — by ambulance if the person is a young child, elderly, pregnant, has heart disease, or develops severe cramping, chest or abdominal pain, vomiting or breathing difficulty. Hospitals treat latrodectism with pain relief, muscle relaxants and, in severe cases, widow antivenom, which works against all North American widow species. Bring the spider or a photograph. Do not cut, suck, burn or apply a tourniquet, and do not rely on home remedies.
Ecological importance and behaviour of the northern black widow
The northern black widow is solitary, nocturnal and profoundly sedentary: a female may spend her entire adult life in one web, repairing it nightly and abandoning it only if it is destroyed or prey disappears. She hangs inverted at the hub and responds to the specific vibration signature of prey striking a gumfoot line.
Diet: beetles, ants, grasshoppers, crickets, cockroaches, caterpillars, woodlice and other spiders. The gumfoot design is unusually good at catching hard-bodied, ground-walking insects that an orb web would never hold, which makes widows meaningful predators of fire ants and other pests in woodland edges and field margins.
Natural enemies: mud-dauber wasps are the most important — Chalybion and Sceliphron species hunt widows specifically, paralyse them and pack them into mud cells as food for their larvae. Other enemies include assassin bugs, praying mantids, ants raiding egg sacs, centipedes and larger spiders. Birds take wandering males occasionally, but a spider that hides in a crevice all day is a poor target for birds of prey.
Mating: males mature early, spin a small web, then abandon it to search for females, following the pheromone-laced silk of a female's web and courting with a long sequence of plucks and vibrations. Sexual cannibalism does occur, but it is not the rule in this species; the popular image of the female always eating her mate is drawn from Australia's redback, where the male actively somersaults into her fangs. Most male northern black widows leave alive and go looking for another female.
Season: adults are most numerous from late spring through autumn; females overwinter in sheltered retreats and can survive two or three years, while males live only a few months after maturing.
Similar spiders and how to tell them apart
| Spider | How it differs from the northern black widow |
|---|---|
| Southern black widow (L. mactans) | A single, connected red hourglass on the underside and usually no row of red spots on top. Ranges further south and is more likely to be found around buildings. |
| Western black widow (L. hesperus) | Connected or narrowly pinched hourglass; found west of the Great Plains, with no natural overlap with the northern widow. |
| Brown widow (L. geometricus) | Tan to mottled brown with an orange hourglass and a spiky, golf-ball-like egg sac. Warm-climate species, common around buildings in the Gulf states. |
| Red widow (L. bishopi) | Orange-red head and legs with a black abdomen; restricted to Florida scrub and palmetto. |
| False black widow (Steatoda grossa) | Purplish brown, slightly smaller, with a pale crescent on the upper abdomen and never any red hourglass. Mild bite. |
| Steatoda borealis | A northern cobweb spider with a pale T-shaped mark at the front of the abdomen and a pale midline stripe; harmless. |
Quick facts
| Other names | Northern widow, variable widow |
|---|---|
| Distribution | Eastern North America from northern Florida to southern Canada, west to eastern Texas, Oklahoma and Kansas |
| Habitat | Undisturbed woodland edges, stumps, hollow logs, brush and rock piles, stone walls, low shrubs, sheds and outbuildings |
| Diet | Beetles, ants, crickets, grasshoppers, cockroaches, woodlice and other spiders |
| Lifespan | Females up to about three years; males only a few months after maturing |
| Predators | Mud-dauber wasps, assassin bugs, mantids, centipedes, ants and larger spiders |
| Web | Strong irregular tangle with sticky gumfoot lines anchored to the ground or a solid surface |
| IUCN status | Not evaluated; widespread but patchy and rarely abundant |
Did you know?
- The species name variolus refers to the pock-like spotting on the abdomen — the same Latin root that gives us variola, the old name for smallpox.
- It is the only widow spider that reaches the Canadian provinces in any number, which makes it the northernmost member of a genus otherwise built for warm climates.
- Widow silk is among the toughest biological materials known, and the coarse gumfoot lines are strong enough to hold a struggling beetle several times the spider's weight.
- The common name has nothing to do with this species in particular: it was applied across the genus because of sexual cannibalism, which is far rarer in northern black widows than the name suggests.
- Antivenom raised against the southern black widow neutralises the venom of every North American widow, including this one, because their toxins are so closely related.
In summary, the northern black widow is a woodland spider of stumps, walls and brush piles, identified by two separate red marks instead of one hourglass and a row of red spots on her back. Treat her with respect rather than fear: keep hands out of dark crevices, wear gloves in the woodpile, and get medical help promptly if a bite happens.
Frequently asked questions about the northern black widow
How do you identify a female northern black widow?
Look at the underside of the abdomen. A female northern black widow is glossy black, about 9–11 mm long, and her red hourglass is split into two separate triangles with black between them. She usually also has a row of red spots down the top of the abdomen and pale diagonal bands on each side.
What is the difference between northern and southern black widows?
The marking is the key. The southern black widow has one connected red hourglass beneath the abdomen; the northern has two separate red marks and normally a line of red dorsal spots. The northern species also ranges much further north, reaching southern Canada, and is more a woodland spider than a house spider.
How can you tell a male northern black widow from a female?
Males are only 4–5 mm long, about half the female's length, and they are not black. They are grey, tan or brown, long-legged, with four pale diagonal bands on each side of the abdomen and small red spots. Juveniles of both sexes look like males and darken as they mature.
How dangerous is a northern black widow bite?
It is medically significant. The venom contains alpha-latrotoxin and can cause latrodectism — spreading muscle cramps, sweating, raised blood pressure, nausea and severe pain. Most healthy adults recover in one to three days with hospital treatment. Deaths are extremely rare, but young children, older adults and people with heart disease are at higher risk.
Is widow venom really stronger than a rattlesnake's?
Drop for drop it is more toxic in laboratory tests on mice, but that comparison is misleading. A widow injects a few micrograms of venom while a rattlesnake delivers hundreds of milligrams. The dose decides the danger, which is why widow bites are painful and frightening yet very seldom fatal.
What should I do if a northern black widow bites me?
Wash the bite with soap and water, apply a cold pack and keep the limb still, then seek medical assessment. Call emergency services if the patient is a young child, elderly or pregnant, or if severe cramping, chest or abdominal pain, vomiting or breathing trouble develops. Take a photo of the spider and never cut, suck or heat the wound.
Are northern black widows aggressive?
No. They are shy, slow-moving and almost blind outside the web, and their instinct when disturbed is to freeze, drop or play dead. Nearly every bite occurs when the spider is trapped against skin — in a glove, a boot, bedding or a hand pushed into a woodpile — rather than through any attack.
How many eggs does a northern black widow lay?
Each pale, papery sac normally holds around 100 to 400 eggs, and a female may make several sacs through the summer, so she can produce well over a thousand young in a season. She hangs the sacs in her web and guards them; incubation takes roughly two to four weeks.
Do the spiderlings stay with their mother?
No. They hatch inside the sac, moult once and leave within days to a couple of weeks. The mother does not feed them, and crowded siblings quickly begin eating each other, so they disperse fast — many by ballooning on a strand of silk. Only a small fraction reach adulthood.
Where are northern black widows usually found?
They prefer undisturbed, sheltered spots at woodland edges: old stumps, hollow logs, brush and rock piles, stone walls, the base of shrubs, and quiet human structures such as sheds, barns, outhouses and woodpiles. They rarely establish inside occupied homes, which is why encounters are uncommon.
References
- World Spider Catalog (2026). Latrodectus variolus Walckenaer, 1837. Natural History Museum Bern. wsc.nmbe.ch/spec-data/45691/taxon
- Centers for Disease Control and Prevention — Venomous Spiders: workplace safety and health topics. www.cdc.gov/niosh/topics/spiders
- Vetter, R. S. & Isbister, G. K. (2008). Medical aspects of spider bites. Annual Review of Entomology 53: 409–429. doi.org/10.1146/annurev.ento.53.103106.093503
