False Black Widow — The One People Actually Find

This is the spider people mean when they say black widow

Round body, glossy and dark, hanging upside down in a messy tangle of web in the corner of a garage. It looks exactly like the photograph everybody has in their head, and in Whatcom County it is almost never the animal in that photograph.

The Washington State Department of Health is direct about it: false black widow spiders, Steatoda grossa, are common in Washington, they closely resemble female black widow spiders, and they are all black without the red markings on the abdomen that a true widow carries.

We get photographs of this spider constantly, and the call almost always opens the same way — somebody has found a black widow in the garage and wants to know what to do about the children, the dog, the firewood pile. The answer is nearly always that it is this instead, and that the correct response is considerably less dramatic than the one they were braced for.

That does not make the question silly. Two spiders that look this similar, with very different reputations, is exactly the situation where somebody should ask.

Telling a false widow from the real thing

One check settles it, and it is not the one most people try.

Look underneath. A true black widow carries a red hourglass on the underside of the abdomen, and she always has it. The false black widow has no red marking at all. If you can get the spider over a sheet of glass, or photograph it from below through a jar, that single view ends the question.

The other differences, in descending order of usefulness:

• Markings on top. Penn State Extension describes the false widow’s abdomen as purplish-brown to black with pale-yellow to grayish markings that are often faded. A black widow is uniformly glossy jet black on top.
• Body shape. The false widow’s abdomen is more oval; a black widow’s is close to a sphere.
• The front half. Penn State notes the false widow’s cephalothorax — the front body section — is reddish-brown with slightly darker legs. A widow is black throughout.
• Size. Penn State puts the female false widow at 6 to 10.5 mm of body, which is smaller than a mature black widow female.
• Shine. A black widow is lacquered. A false widow is duller, often almost matte.

The web is no help whatsoever. Both build the same kind of irregular, three-dimensional tangle, and nobody should try to identify either from it.

Are there black widow spiders in Washington state?

Yes, and almost certainly not where you are standing.

The health department describes black widows as common to eastern Washington, with a few small populations west of the Cascades. It is a dry-country animal and the eastern half of the state suits it. The western half, and Whatcom County in particular, does not.

Our own position is narrower than the state’s and worth stating as our own experience rather than as a fact about the county: in our work here we do not find them, and we do not get calls that turn out to be one. Every single suspected widow we have been sent a photograph of has been something else — this spider, a young orbweaver, or a cellar spider.

That is not the same as never. Spiders travel in freight, firewood, plant deliveries and moving loads, and the state’s own wording allows for small western populations. So the honest framing is: a western Washington black widow is possible rather than expected, and if you are east of the mountains and find one in the garage, take it seriously.

The wider version of this question, including every other spider that turns up here, is in common spiders in Washington state.

Does a false black widow bite?

It can, and this is the part where we are going to be less reassuring than most pages on this site.

The Washington State Department of Health says false black widow bites do happen, and that the venom is much less toxic than a black widow’s. Penn State Extension goes further and describes what a bite actually does: symptoms similar to a true widow bite but far less severe, blistering at the site, malaise lasting several days, moderate to severe pain that may build through the first hour, and occasional nausea, headache and lethargy. Recorded symptom duration runs from one hour to sixty.

So: not a medical emergency, not a spider to be frightened of, and not nothing either. A bad few days is a fair description of the worst of it.

What makes a bite happen is the same thing that makes nearly every spider bite happen — the spider was pressed against skin. Inside a glove left in a garage, in a boot in a crawlspace, in bedding or clothing taken from storage, under a hand reaching blindly behind stored boxes. Wearing gloves to move a woodpile or clear an outbuilding corner removes most of the realistic exposure there is.

If a bite blisters badly, spreads, or you feel properly unwell, see a doctor. Not because this spider is likely to be the cause of anything serious, but because skin infections are common, they are treatable, and they are the thing most often mistaken for a spider bite.

The British false widow stories are about a different spider

Worth addressing head-on, because people arrive here having read them.

Every few years the British press runs a wave of coverage about false widow spiders closing schools and putting people in hospital. That coverage concerns Steatoda nobilis, the noble false widow, which is a different species from the one in Washington garages and is not established here — US records for it are from California.

The Burke Museum, which is the arachnology authority for this state, keeps a page on exactly this. It traces the panic to a 1998 conservation brochure that wrongly called the species the one British spider whose venom could cause people discomfort, through a 2006 interview, into what the museum describes as a flood of misinformation by 2015. It notes that reported bites frequently show the symptoms of infection rather than of venom, and that the spider is often never seen at all.

One line in that page is worth a pest control company repeating against its own interest: the museum observes that expert quotes in those stories often come from pest control operators rather than from arachnologists. That is a fair criticism of this trade, and the correct response to it is to cite the museum rather than ourselves, which is what this page does.

Where they live, and the one genuinely interesting thing about them

Low, undisturbed, and indoors all year.

Penn State Extension describes all life stages being found indoors year-round in homes and other structures, with outdoor populations under bark, in rock crevices, on low foliage and under bridges. In a Whatcom County property that means garages, crawlspaces, basements, window wells, the back of a shed, behind a water heater, underneath stored boxes that have not moved in a year.

Females can live up to six years, which is unusual and explains something people notice — the same corner of the same garage is occupied season after season, and it is sometimes the same animal. Mating happens in spring, and females produce three or more egg sacs from May through July, each holding a couple of hundred cream-colored eggs.

And the genuinely interesting part: Penn State records that they prey on other spiders, including true black widows. We mention it because it is sourced, and because it is a pleasing fact about an animal most people want to kill on sight.

There are several other things said about this spider online that we are not going to repeat, because we could not find anybody credible saying them.

Black spiders in Washington, in order of likelihood

If you have found a dark spider in this county, this is roughly the running order.

1. Giant house spider — if it is large, fast, long-legged and running across a floor. By far the commonest.
2. False black widow — if it is round-bodied, glossy, hanging in a tangled web low in a garage or crawlspace.
3. Cross orbweaver, dark variants — if it is sitting in a wheel-shaped web outdoors in late summer.
4. Cellar spider — if it is small-bodied with very long thin legs in a ceiling corner.
5. Hobo spider — possible, indistinguishable from a giant house spider without a microscope, and harmless either way.
6. Wolf spider — if it is hairy, striped and outdoors on the ground.
7. Black widow — essentially never, on this side of the mountains.

There is a longer version of this list, with the reasoning, in the spiders in Washington state guide.

What we do about them

Usually nothing, and the call usually ends on the phone.

Most false widow contacts are identification. Somebody sends a photograph, we tell them what it is, and that is the end of it. We would rather spend ten minutes on that than sell a treatment to somebody who found one spider in a garage.

Where there is real work:

• A genuine population in a garage, crawlspace, outbuilding or window wells, with webbing and numbers somebody is living with.
• A household where somebody is frightened of spiders to a degree that affects how they use their own home. That is a legitimate reason and we do not treat it as a silly one.
• A property where people reach blindly into undisturbed spaces — woodpiles, storage, a workshop — where the sensible answer is partly gloves and partly reducing harborage.

What that work looks like, and what it honestly achieves, is set out on spider control. The short version is that spider treatments are less effective than people expect and sealing, lighting and clutter reduction do more.

What we will not tell you

That you have black widows. We do not find them on jobs in this county, and saying otherwise would sell a lot of treatments.

That a false widow bite is harmless. It is not dangerous, and it can still ruin a few days, and the Penn State description above is what we are going on.

That the British newspaper stories apply here. They are about a species that does not live in Washington, and the Burke Museum has already taken that one apart properly.

Or that you need a quarterly program because of one spider in a garage. Send a photograph instead — from above and from underneath if you can manage it. We will tell you what it is for nothing, and most of the time the answer is this one and nothing needs doing.