Brown Recluse or Wolf Spider? Size Settles It

The wolf spider is the large, fast, hairy spider that runs across a basement floor and gets photographed in a state of some alarm. It is also the animal most often reported as a brown recluse, which is odd, because the two look nothing alike once you know what to compare.

1. Size — the test that resolves most cases

Brown recluse: body about the size of a pea, roughly 6 to 12 mm. Legspan about a US quarter.

Wolf spider: body from a thumbnail up to a matchbox. Legspan commonly over two inches, and in the largest species well over three.

If the spider made you take a step back on the strength of its size alone, it is not a recluse. Recluses are unremarkable to look at, which is part of why they get missed.

2. Pattern — plain versus busy

Brown recluse: uniformly light-to-medium brown with no pattern at all on the abdomen. Genuinely plain. The only marking is the darker violin shape on the head-and-thorax.

Wolf spider: boldly patterned in browns and greys, with lengthwise stripes on the head-and-thorax and chevrons or dashes on the abdomen. Mottled and busy.

A patterned abdomen rules out a recluse immediately.

3. Legs — banded versus plain

Brown recluse: legs plain, fine-haired and completely unbanded. No rings, no stripes, no visible spines.

Wolf spider: legs thick, obviously bristly, and usually banded with darker rings.

This is the best single check after size, and it works even in a poor photograph.

4. Eyes — the definitive test

Brown recluse: six eyes in three pairs, arranged in a wide arc.

Wolf spider: eight eyes in three rows, with two very large forward-facing eyes that dominate the face.

The wolf spider's big eyes have a practical consequence you can use in the dark: shine a torch across a lawn at night, hold it beside your temple, and wolf spider eyes reflect back as bright green points, sometimes dozens at once. Recluses do not do this.

5. The web

Brown recluse: builds a small, irregular, sticky retreat web in an undisturbed corner. It is a hideout, not a trap.

Wolf spider: builds no catching web at all. It is a running hunter.

If the spider was sitting in a web, it was not a wolf spider. If it was running across the floor, that fits a wolf spider far better than a recluse — recluses are nocturnal and secretive and are usually found in stored boxes and clothing rather than sprinting across open ground.

Quick reference

The egg sac giveaway

If your spider was carrying a round grey ball attached to the rear of its abdomen, or was covered in dozens of tiny spiderlings, it is a wolf spider and nothing else. Female wolf spiders attach the egg sac to their spinnerets and drag it around, then carry the newly hatched young on their back for a week or more. No other North American spider does this.

Where the confusion comes from

Wolf spiders are common, they come indoors in autumn, they run fast, and they are big enough to be frightening. Fear plus a brown spider plus a name people have heard of produces a recluse report.

It is worth pushing back on, because wolf spiders are among the most useful predators in a garden, and because the anxiety is misplaced — in most of the country there are no recluses at all.