Spider Identifier

Photograph the spider and get a plain answer: what it is, whether it can hurt you, and what it’s commonly mistaken for.

Drop a photo of the spider, or use your camera.

Know That Bug never stores the photo. Our in-process copy is discarded after the answer; we keep the answer and a one-way hash, never the image.

The ones worth ruling out first

Only a handful of spiders in the US are medically significant. Nearly every “brown recluse” turns out to be something else — so these pages lead with what separates them, not with taxonomy.

What it probably is instead

How to photograph a spider so it can be identified

Most failed identifications are failed photographs. Four things make almost all the difference:

Side-on, whole animal in frame. Leg length and body proportion carry more information than colour, and a top-down shot hides both.
Something for scale. A coin, a fingertip, a tile edge. Size separates more species than almost anything else and is the hardest thing to judge from a photo.
Use the flash, even in daylight. It freezes movement and lifts the leg banding and abdominal markings that the answer usually turns on.
If you can safely shoot the front of the head, do. Eye arrangement is the single most reliable character in the whole group.

Identifying a spider without a photo

You can get a long way on the web alone, because web architecture is close to family-level identification:

Neat circular orb, rebuilt often. An orb weaver — the yellow garden spider or the banana spider. Harmless.
Messy tangle in a corner. A cobweb spider. Mostly the common house spider, but widows build the same shape lower down.
Flat sheet with a funnel at one edge. A funnel weaver — the barn funnel weaver almost everywhere, the hobo spider only in the Pacific Northwest.
Loose tangle on a ceiling. A cellar spider. Harmless and genuinely useful.
No web at all. A hunter — wolf spider, jumping spider, or yellow sac spider.

How to tell a brown recluse from everything else

The reliable character is the eyes: a recluse has six eyes in three widely spaced pairs, where almost every other spider has eight. The violin marking is far less reliable than its reputation — several harmless species have something similar, and on a dark or worn individual it can be invisible.

The other giveaway is the legs. A recluse’s legs are uniformly coloured, bare and without spines. If the legs are banded, stripey or obviously hairy, it is not a recluse.

Range settles more cases than either. The brown recluse occupies the south-central states — roughly Kansas and Texas east to Georgia. It is genuinely absent from California, the Pacific Northwest and most of the northeast, despite being reported from all of them constantly. See the full record, or compare against the southern house spider and the woodlouse spider, which has six eyes too and is the one case where the eye rule alone is not enough.

How to tell a widow

The marking is on the underside, which is why widows get missed: they hang upside-down in the web, and from above there is often nothing to see. A glossy black spider with a round abdomen in a tangled web at ground level deserves a careful look before you reach past it.

Not all widows are black. The brown widow is tan and mottled with an orange hourglass, and it is regularly written off as a house spider. Its egg sac settles it instantly — a silk ball covered in spikes is a brown widow and nothing else. The false widow is the common false alarm: similar shape, purplish-brown, no hourglass, and not medically significant.

Where you found it narrows it fast

Ceiling corner, indoors. Cellar spider or common house spider. Both harmless.
Running across the floor at night. A funnel weaver or a wolf spider — and worth knowing that recluses and funnel weavers both climb badly, so a spider high on a wall is unlikely to be either.
Woodpile, meter box, under garden furniture. Widow territory. Wear gloves.
Stacked cardboard, stored clothing, a shoe. The classic recluse situation, inside its range.
Big web across a garden path. An orb weaver. Harmless, and it will rebuild elsewhere if you clear it in the evening.

Common questions

Why do I suddenly have spiders in autumn?

Mature males wander looking for mates in late summer and autumn. The population has not exploded — the males have simply started walking around in the open, which is when people notice them.

Can you identify a spider from a bad photo?

Sometimes, at a coarser rank. We answer at the most precise level the photograph honestly supports, so a blurry shot may get a family rather than a species — and we will say which.

Is it a spider at all?

Count the legs. Six means an insect, including the spider cricket, which is a cricket and is one of the most common false spiders people report. Antennae also settle it — no spider has them.

Should I kill it?

There is rarely a reason to. Most house spiders eat the insects you would rather not have, and cellar spiders eat other spiders. Glass and card puts anything outside in a few seconds.

When we can’t tell you

Plenty of photographs simply don’t contain the answer. If the eyes aren’t resolvable, no identifier — ours or anyone else’s — can separate a recluse from a funnel weaver, and we would rather say so than guess. Where an answer lands in a group that recluses or widows are mistaken for and the photo can’t rule them out, you get an explicit “we can’t rule this out” rather than a harmless verdict.

We publish what we get right and wrong with real numbers, measured against 168 expert-verified photographs.