Brown Widow (Latrodectus geometricus)
The brown widow is the black widow's quieter, faster-spreading cousin: a tan, patterned spider with an orange hourglass and an egg sac covered in silk spikes. It has colonised warm regions on every inhabited continent, it often outnumbers black widows in towns and cities, and although its venom is every bit as potent, its bites are usually far milder.
By Dr. James WatuwaPublished August 6, 2019Updated September 13, 2026✓ Reviewed by Dr Richard J. Pearce (PhD)
In this guide
Physical description and identification
A brown widow has the same silhouette as any widow — a globe-shaped abdomen on long, fine legs — but none of the black widow's stark simplicity. The body is patterned rather than plain, and the giveaway is underneath: an hourglass in orange or yellow-orange rather than red.
Adults
- Size: females measure about 7–12 mm in body length with a leg span of 30–50 mm (1.2–2 in). Males are roughly a third of the female's length at 3–5 mm.
- Colour: the ground colour ranges from pale sandy tan through grey-brown to almost black. Typical individuals carry a mottled dorsal pattern of white, cream, brown and black blotches with a row of dark side spots, and the legs are clearly banded light and dark. Very dark specimens lose most of the pattern and are easily mistaken for a southern black widow — check the underside and the legs.
- Hourglass: orange to yellow-orange, occasionally reddish-orange, and usually complete. A red hourglass on a plain black body is a black widow; an orange hourglass on a banded-legged brown body is this species.
- Eyes and comb: eight small eyes in two rows of four, and the serrated comb of bristles on the fourth leg that all cobweb spiders use to throw silk over prey.
Eggs and egg sacs
The egg sac is the best identifier in the genus. It is tan to grey and covered in fine silk spikes, so it looks like a tiny sea mine or a woolly burr, quite unlike the smooth papery sacs of the black widows. Each holds roughly 100 to 150 eggs, and a female may build a dozen or more, so an established site often carries several sacs of different ages. Spiderlings emerge after two to four weeks.
Spiderlings
Emerging spiderlings are pale with dark leg joints and take on the adult pattern within a few moults. Crowding in the web leads to some sibling cannibalism, but most of the brood disperses quickly, walking away along silk lines or ballooning on the wind. That output, plus a tolerance for dry man-made surfaces, is why the species colonises a new city so fast.
The web
The web is a small, untidy three-dimensional tangle with a silk retreat at one edge where the female sits with her egg sacs, and sticky vertical lines anchored below it to catch walking insects. Brown widows are strikingly urban in their choice of site: the underside of patio furniture, the rims and drain holes of plant pots, mailboxes, utility boxes, storage bins, playground equipment, fence rails and the wheel arches of parked cars. They favour narrow, hard-edged cavities and use dozens of them along a single suburban street. Our guide to spider webs covers how these gumfoot snares work.
Where the brown widow lives
The brown widow's original home is still debated. It was long assumed to be South Africa, where it is a familiar garden spider, but genetic work points to an African origin with a long history of human-assisted spread, and South America has also been proposed. What is certain is that it is now pantropical, established across warm parts of Africa, the Middle East, Asia, Australia, the Pacific, the Caribbean and the Americas.
In the United States it was first recorded in Florida in 1935 and remained a Gulf Coast curiosity for decades. From about 2000 it expanded rapidly: it reached southern California around 2003 and is now abundant there, and it occurs through Texas, Louisiana, Georgia, the Carolinas and Hawaii. It does not survive hard freezes, so its northern limit is set by winter temperatures.
Habitat is overwhelmingly human: brown widows are far more common in gardens, car parks and school grounds than in natural vegetation, and dozens of adults on a single property is normal where the species is established.
Are brown widow spiders venomous?
Yes, and this is the point most often reported incorrectly. Brown widow venom contains the same alpha-latrotoxin as black widow venom and in laboratory tests is at least as potent, in some assays more so. The common claim that the brown widow's venom is weak is simply wrong.
What differs is the dose and the delivery. The brown widow has smaller venom glands than a black widow, and clinical experience — including a well-known South African series of verified bites — shows that it tends to inject very little, often producing no more than pain and redness at the site. Systemic latrodectism, the cramping, sweating whole-body syndrome typical of black widow envenomation, is uncommon after a brown widow bite but not impossible. The correct summary is a potent venom delivered in a small dose, which usually adds up to a mild bite.
Can brown widow spiders bite?
They can, but they are notably reluctant. A brown widow disturbed in her web typically drops, pulls her legs in and stays motionless rather than defending herself, and is considered less prone to bite than a black widow. Bites happen when the spider is pressed against skin — a hand under a patio chair, fingers around a plant pot rim, a spider inside clothing left outside.
Symptoms. Most reported bites cause a sharp pinprick followed by local pain, redness and mild swelling that fade within a day or two. A minority produce more: muscle cramps spreading from the bite, sweating, nausea, headache and raised blood pressure, usually beginning within an hour and settling over one to three days. No deaths have been attributed to this species.
What to do. Wash the site with soap and water, apply a cold pack and take a simple painkiller. Photograph the spider if you safely can. Seek medical care if cramping spreads beyond the bite, if sweating, vomiting or chest pain develop, or if the person bitten is a young child, elderly, pregnant or has heart disease — the antivenom used for black widow envenomation works against Latrodectus venom generally. Do not cut, suck, apply a tourniquet or apply heat, and skip the home remedies; none of them help.
Black widow or brown widow? Look at three things. The hourglass: red means black widow, orange or yellow means brown widow. The legs: plain black, or banded light and dark. And the egg sacs, if any are present — smooth and papery for a black widow, spiky and tufted for a brown widow. The egg sac alone settles it.
Ecological importance and behavior of the brown widow
Brown widows are sedentary trap-builders. The female hangs in her retreat by day, moves onto the web at dusk to rebuild the sticky lines, and rarely leaves a good site. Prey is mostly walking insects — ants, beetles, cockroaches, woodlice and crickets — which is why they concentrate where insects travel along hard edges.
Natural predators: mud dauber and digger wasps are the main specialists, paralysing widows to stock their nests; spider wasps, mantises, geckos, ants and larger spiders also take them, and parasitoid wasps attack the egg sacs.
Competition with black widows: one of the most studied things about this species is what happens when it arrives. In urban southern California the brown widow has largely displaced the western black widow from gardens and buildings, partly by sheer reproductive output and partly because brown widows eat black widow eggs and juveniles. The black widows persist in natural habitat nearby.
Season and lifespan: in frost-free regions brown widows breed year round, peaking in warm months. Females live roughly one to one and a half years and keep producing egg sacs throughout; males survive only weeks to a few months after their final moult. Unusually for the genus, males often remain in or beside a female's web after mating.
Relationship with humans: the species is beneficial in principle and a nuisance in practice, because its favourite sites are the ones people reach into blind. Wear gloves for garden work, tip and check plant pots and stacked furniture, and knock down webs and egg sacs on play equipment and doorways. Removing the sacs matters more than killing the adult, since each one is another hundred spiders.
Similar spiders and how to tell them apart
| Spider | How it differs from the brown widow |
|---|---|
| Southern black widow (Latrodectus mactans) | Glossy, unpatterned black with plain black legs and a red hourglass; smooth papery egg sac. Bites far more often cause full latrodectism. |
| Western black widow (Latrodectus hesperus) | Also plain glossy black with a red hourglass. Shares gardens and buildings with the brown widow across the southwestern US, usually in lower numbers. |
| Redback (Latrodectus hasselti) | Black with a bold red or orange stripe along the top of the abdomen as well as a ventral hourglass. Australian, and medically significant. |
| False black widow (Steatoda grossa) | Matt purplish brown with a pale crescent at the front of the abdomen, no hourglass and unbanded legs. Harmless. |
| Brown recluse (Loxosceles reclusa) | Uniform tan, six eyes in three pairs, a violin mark and long smooth legs; no tangle web and no hourglass. |
Quick facts
| Other names | Brown button spider, geometric button spider, grey widow |
|---|---|
| Distribution | Pantropical — Africa, the Middle East, Asia, Australia, the Pacific, the Caribbean and the Americas |
| Habitat | Patio furniture, plant pots, mailboxes, utility boxes, fences, storage bins, playground equipment, parked vehicles |
| Diet | Ants, beetles, cockroaches, woodlice, crickets and other ground-level arthropods |
| Lifespan | Females about 1–1.5 years; males weeks to a few months |
| Egg sac | Tan, spike-covered, roughly 100–150 eggs; many sacs per female |
| Predators | Mud daubers, digger wasps, mantises, geckos, ants |
Did you know?
- The name geometricus refers to the geometric blocks of colour on the abdomen, which also gave southern Africa the name "geometric button spider".
- The spiky egg sac is unique among the widows and is used to map the spider's spread, because a sac can be identified from a photograph even with no adult present.
- Brown widows were first collected in the United States in 1935 but only became abundant after 2000 — a long lag between arrival and explosion that is common in introduced spiders.
In summary, the brown widow is a widow spider that has traded danger for numbers. Its venom is fully potent, but it bites rarely and injects little, so the practical risk is low while the encounter rate is high. Learn the orange hourglass, the banded legs and above all the spiky egg sac, and you can tell at a glance which widow you have.
Frequently asked questions about the brown widow
What colour is a brown widow's hourglass?
It is orange to yellow-orange, occasionally with a reddish tint, and sits on the underside of the abdomen. A bright red hourglass on a plain glossy black body belongs to a black widow instead. The brown widow's banded legs and mottled back pattern confirm the identification from above.
How do you identify a brown widow egg sac?
The sac is tan to grey and covered in fine silk spikes or tufts, so it looks like a small woolly burr or sea mine. No other widow makes one like it — black widow sacs are smooth and papery. Each holds roughly 100 to 150 eggs, and a female may build a dozen or more.
How big do brown widow spiders get?
Adult females are about 7 to 12 mm in body length with a leg span of 30 to 50 mm, roughly 1.2 to 2 inches across. Males are much smaller, about 3 to 5 mm, or a third of the female's length, and are rarely noticed.
Is brown widow venom weaker than black widow venom?
No. The venom contains the same alpha-latrotoxin and is at least as potent in laboratory tests. Brown widow bites are usually milder because the spider has smaller venom glands and tends to inject very little, so most bites cause local pain and redness rather than full latrodectism.
Are brown widow spiders aggressive?
No. A disturbed brown widow usually drops out of the web, curls her legs and plays dead rather than defending herself, and she is considered less likely to bite than a black widow. Bites almost always occur when the spider is pressed against skin, for example under a patio chair or a plant pot rim.
What should I do if a brown widow bites me?
Wash the area with soap and water, apply a cold pack and take a simple painkiller. Seek medical care if cramping spreads beyond the bite, if sweating, vomiting or chest pain develop, or if the person is a young child, elderly, pregnant or has heart disease. Never cut, suck or apply a tourniquet.
Where do brown widow spiders build their webs?
Almost always in narrow man-made cavities near the ground: under patio furniture, in the rims and drain holes of plant pots, inside mailboxes, utility and irrigation boxes, storage bins, fence rails, playground equipment and the wheel arches of parked cars. They are far more common in gardens and car parks than in wild vegetation.
Are brown widows replacing black widows?
In urban areas of the southwestern United States, largely yes. Brown widows reproduce faster, tolerate man-made surfaces better and will eat black widow eggs and juveniles, so they dominate gardens and buildings while black widows persist in surrounding natural habitat.
Do brown widow spiderlings eat each other?
Some do. Crowding in the web after they emerge leads to a degree of sibling cannibalism, but it is not universal and most of the brood disperses within days by walking along silk lines or ballooning on the wind. High egg output rather than sibling survival is what drives the population.
How do I keep brown widows off my patio?
Check and tip plant pots, stacked chairs and storage bins before handling them, wear gloves for garden work, and sweep webs and egg sacs off furniture, doorframes and play equipment regularly. Removing the spiky egg sacs matters more than killing adults, since each sac represents another hundred or more spiders.
References
- World Spider Catalog (2026). Latrodectus geometricus C. L. Koch, 1841. Natural History Museum Bern. wsc.nmbe.ch/spec-data/45671/taxon
- 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
