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What spider is this? Almost certainly a harmless one.

Of roughly 3,500 spider species in the United States, only two groups matter medically: widows and recluses. Everything else is a spider you can safely ignore. Start with the web — its shape is fixed by family, so it narrows the list faster than anything else — then add size, location and markings.

Identify this spider Do brown recluses live where I do?

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Two medically significant groups, out of ~3,500
Range checked by state
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1.Was there a web, and what shape?

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The most informative question. Web architecture is fixed by family, so it separates the big groups immediately — and it rules out recluses and widows faster than anything else.

2.Which state are you in?

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Matters more than you would expect. Brown recluses are absent from most of the country, including California, Florida and the entire northeast.

3.How big was the body?

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Body only, not counting the legs. Neighbouring sizes stay on the list, because everyone overestimates.

4.Where did you find it?

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Indoor and outdoor spiders barely overlap, so this cuts the list roughly in half.

5.Any distinctive markings?

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A red hourglass underneath means a widow and nothing else. A violin shape is suggestive of a recluse but far from conclusive — several harmless spiders have similar marks.

6.Did it do any of these?

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Behaviour separates families cleanly. Jumping means a jumping spider; eyes reflecting a torch beam means a wolf spider.

7.What colour was it?

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Last, and it never removes anything from the list — spider colour varies with age, moult stage and light.

30 possibilities

Answer any question to begin

6 medically significant species are still on this list

The mix-ups that cause the panic

Four questions account for most alarmed spider searches, and all four have reassuring answers.

If you think you were bitten

Most suspected spider bites are not spider bites. Studies of patients presenting with a “spider bite” repeatedly find that the large majority are bacterial skin infections — frequently MRSA — which need antibiotics rather than reassurance. A spreading, painful, pus-filled sore is far more likely to be an infection than a spider.
Wash it, ice it, and watch it. Clean the area with soap and water, apply a cold pack, and keep an eye on it.
Get medical care if the wound spreads or darkens, if you develop cramping, sweating, fever or severe abdominal pain, or if you are confident it was a widow or a recluse.
Bring the spider only if it is already dead and to hand. Do not go looking for it. Doctors treat symptoms, not species.

In the US, the Poison Help line is 1-800-222-1222. This site is a reference, not medical advice.

Spiders in your state

Which species live near you, and whether widows or recluses are among them.

Four web shapes, and what each one rules out

Neither medically significant group builds a patterned web. Widows make an untidy three-dimensional tangle with a dense funnel-shaped retreat; recluses make a small, scruffy, irregular sheet in undisturbed dark. A neat wheel in a doorway is an orb weaver, and an orb weaver has never sent anyone to hospital.

Questions people ask

How can I tell if a spider is dangerous?

Only two groups of US spiders are medically significant: widows and recluses. Widows are glossy black with a red hourglass on the underside and sit in a messy tangle web. Recluses are small, plain, uniformly light brown with unbanded legs and six eyes, and only occur in the midwest and south-central states. This site covers 6 such species; every other spider you meet is harmless.

Do brown recluses live in California?

No. Verified brown recluse populations do not exist in California despite frequent reports. The desert recluse occurs in undisturbed desert habitat in the far southeast of the state, away from urban areas. Most suspected recluse bites in California turn out to be bacterial infections.

Where recluses actually live →

Are daddy long-legs the most venomous spider?

No, and the name refers to three different animals. Harvestmen are not spiders at all and have no venom glands or fangs. Cellar spiders are spiders with unremarkable venom and fangs that can pierce skin, producing only a faint sting. Crane flies are insects. None are dangerous.

Where the myth came from →

Is there an app that identifies spiders from a photo?

Yes — Bug Identifier+, and this site is its free web companion. The honest split: a photograph is often enough for a large, distinctive spider, and rarely enough for the small brown ones people worry about most. The key here starts with where you live, which eliminates more possibilities than any photo can.

Is this site free?

Yes — the key, every spider page and every state page, with no account and no email. Nothing you pick is sent anywhere. The app is a free download for photo identification and offline reference.

I was bitten by a spider — can an app tell me what bit me?

No, and neither can a doctor from the wound alone. Spider bites are diagnosed from the spider, not the mark, and the large majority of "spider bites" people present with turn out to be skin infections, most often MRSA. If a lesion is spreading, painful, or you feel unwell, that is a reason to see a doctor promptly — not a reason to identify a spider.

What the bite marks actually tell you →