Black widow or no?

July 20, 2007 11:12 PM

Black widow or no? (Sorry, no photo -- phone was dead, so couldn't take a pic. But perhaps some of you spider buffs can help me out nevertheless.)

Earlier tonight, I killed (please no lectures about killing spiders - my boyfriend's dog is in the house and will eat such things) what I thought might be a black widow, but based on what I've been reading, some of the characteristics have me a bit unsure. Perhaps it was a juvenile or male black widow, or perhaps another species entirely?

- about 3/8 to 1/2 inch long (which seems on the small size?)
- glossy, jet black (which seems typical)
- abdomen not hugely bulbous -- more oval-shaped (which doesn't seem typical)
- definite orange marking (which seems typical, even if red is more common), but on the back, not underside (which doesn't seem typical)
- all legs of even length (which doesn't seem typical)

We live in L.A.; my boyfriend says he sees nests of them pretty often outside at night when he's walking the dog, but never indoors (this was in his bathroom -- he's at work so wasn't around to ID it). How freaked out should we be?

posted by scody to science & nature (17 comments total)

How freaked out should we be?

Not very, even if it was a BW, unless you got bit.

There was a creepy story of a fellow finding one (and getting bitten by it) in the second half of a bag of grapes he had in the fridge as he sat down to eat them in front of the tv on CBC the other night.

Was it a BW? dunno, have you looked through something like this.
posted by edgeways at 11:26 PM on July 20, 2007

incidentally, while they are poisonous and the bites hurt, they are rarely fatal and the spiders are not aggressive.
posted by edgeways at 11:28 PM on July 20, 2007

have you looked through something like this.

Yep, that's why I'm asking. The spider I saw looked very much like those, EXCEPT that the legs were somewhat shorter and more even all around, and the abdomen was not nearly so bulbous. Plus the marking was on the back, not the underside.
posted by scody at 11:36 PM on July 20, 2007

I don't think that widows have the markings on their backs. It was probably a copycat spider.
posted by Addlepated at 11:56 PM on July 20, 2007

I'm thinking what Addlepated is thinking.
see: Batesian Mimicry.
posted by The Esteemed Doctor Bunsen Honeydew at 12:10 AM on July 21, 2007

Black widows only have the hourglass shaped red marking on their underside. If this one had it on the back, it was not a black widow.
posted by chrisamiller at 12:12 AM on July 21, 2007

The description could apply to many spiders, however, one way to narrow it down is to look at the web. Black widows have webs that are usually near the ground, or just off the ground. The webs are characterized by a retreat of sorts where the spider sits, and a tangle of web, with strands leading down to the ground. Each strand is basically glued down to the ground, and under high tension, so when an insect brushes against the strand it snaps back and hauls the insect into the air. So a look at the web should narrow it down. AUstralian black widows do have a marking on the back, and besides the markings vary like crazy anyway.
posted by dhruva at 12:17 AM on July 21, 2007

Maybe a mutant black widow?
posted by brujita at 12:32 AM on July 21, 2007

No web visible; it was marching around the shower (lurking near the conditioner, actually; perhaps "frizzy hair in summer" is also a known characteristic of certain spiders?).

The wikipedia entry indicates that juvenile females can have the marking on their backs rather than undersides, but being that it's wikipedia I don't know how much store to put in that.
posted by scody at 1:49 AM on July 21, 2007

How freaked out should we be?

Don't be freaked out at all, you already killed it.
posted by amyms at 2:35 AM on July 21, 2007

Like this spider?
posted by anaelith at 5:41 AM on July 21, 2007

Perhaps I'm missing something but at least a few of the "black widows" on the page given by edgeways have the red marking on the back, not the underside.
posted by wackybrit at 5:51 AM on July 21, 2007

anaelith: yep, like that, though there was just a single orange mark (fused hourglass shape) without the additional marks on the side (and the legs were solid black, not black and brown as in that photo). Body not quite so globular, though -- a bit more oval-shaped and slender.
posted by scody at 12:08 PM on July 21, 2007

Mark on the back, not a widow. Juvies and males have a nice marbled pattern, I've never seen one with a distinct marking topside. But the good news is that there's no shortage of legitimate widows in and around LA, so you can be as freaked out as you want. But honestly, their prey are bigger public health problems than they are.
posted by Eothele at 8:52 PM on July 24, 2007

Widow spiders are a genus (Latrodectus). The black widow (L. mactans) is one species, and does have the hourglass on the underside of the abdomen; however, other species can have markings on the upper side of the abdomen. There is a Western black widow (L. hesperus), but searches for spider images on the internet are always very dicey (I see a good chunk of my results are in the wrong family altogether). Since it's not a species I know well, I can only really guess that that might be it.

What you describe sounds like a good candidate for Latrodectus. Steatoda is another possibility (same family and they can look like widows). Unfortunately I'm not very familiar with the species on the west coast, and without photos, more precise identification other than some educated guesses is probably not possible.
posted by Tehanu at 8:59 AM on July 25, 2007

The only Latrodectus species you should be finding in LA are hesperus and geometricus. You can look for a while and not find geometricus. If you look for fifteen minutes and you don't find hesperus, you probably didn't look in your fusebox (I'm being glibly hyperbolic- but hesperus is common as dirt, geometricus less so). We'll see whether the species-level distinction between hesperus and mactans withstands scrutiny, but at the looking-at-pictures-on-the-internet level you can think of them as the same thing.

Steatoda wouldn't be jet-black (pics, 1, 2, the white markings are frequently almost invisible). But Tehanu's right, without a good picture no one's going to be able to tell you that it is or isn't anything.

Latrodectus hasselti has a red mark on the other side, but you shouldn't have found it in North America. If you did, we can publish! (I think there are some other species with the mark hither and yon, if you still think it's a possibility, I can call a guy who'll know off the top of his head.)
posted by Eothele at 4:17 PM on July 25, 2007

On the other hand, this guy seems to have found an adult black widow with red markings on its back, and he seems to feel like they're common where he lives. Of course, it's mactans, not hesperus, but like I say, they may or may not be the same thing.

I'm talking to myself, aren't I?
posted by Eothele at 11:04 AM on July 26, 2007