Friday, May 12, 2006

Friday spider blogging

Science (spider) Friday: The Black Widow

As my tribute to Science Friday on Daily Kos, I would like to welcome you to the first weekly edition of Spider Friday--an introduction to the spiders that either do or could affect your daily life. You like science, and I like spiders, so it seems like a perfect match.

Why spiders? Because to me, there is nothing that symbolizes the wonder, diversity, and even the beauty of nature quite like the spider. To me, spiders are the most amazing animals on earth. Imagine if you pulled your house out of your ass every night and then ate it for breakfast the next morning.

So let's get things started with the Black Widow. You think you know the Black Widow--but do you really?


Kingdom: Animalia (Animals)
Phylum: Arthropoda (Arthropods)
Class: Arachnida (Arachnids)
Order: Araneae (Spiders)
Infraorder: Araneomorphae (True Spiders)
Family: Theridiidae (Cobweb Spiders)
Genus: Latrodectus (Widow Spiders)

This Friday, we will be discussing spiders in the Latrodectus genus, including, but not limited to, the Black Widow. But first, some background is in order.


These spiders get their name because of the cannibalistic reputation of the females, who have a reported proclivity toward eating their much smaller mates after sex. The truth is far less interesting, however--while such behavior has been often seen in captivity, it apparently happens much less often in the wild when the male has a better chance to escape (girls, if you really want to know the reason we guys tend to head out in the morning and leave you waking up to a stereotypically empty bed, now you know the reason). While we're on this subject, black widow females also have the capability to store sperm after a mating and can produce more fertilized egg sacs without mating again (girls, another note: don't ever try to develop this capability).

Black widow mating takes place in late spring or summer. The female will then produce an egg sac containing anywhere from 25 to 250 eggs. When the spiderlings emerge from the eggs, they're usually white, as seen in the fascinating picture below:

The spiderlings take a couple of months to mature, growing darker with each successive molt.


Black Widow venom contains a very potent neurotoxin that affects the muscles and the central nervous system. Bites will not initially be felt at first, but they will generally be followed in a few minutes by intense pain at the site of the bite, as well as red dots at the puncture points. This is followed by severe muscle cramping, especially in the legs and abdomen--which can become literally board-stiff some time after the bite (but if you're looking to get washboard abs, believe me--this isn't a good way to do it). Excessive salivation due to loss of gland control is also a common symptom, as well as mild psychological reactions, such as mild anxiety. In more extreme cases, stupor or severe paranoia can be exhibited as a result of Black Widow bites. Black Widow poisoning (also called latrodectism) is typically treated with a combination of antivenin, as well as the muscle relaxant calcium gluconate to counteract the muscle cramping and relieve the associated pain.


And now for the fun part!

Really, it's a misnomer to be talking about the "black widow" at all, because what we commonly term the "black widow" is actually three different species! If you live in the Western United States (essentially the Rockies and further west), what you might see in some dark corner is the Latrodectus hesperus--the Western Widow. But if you live in the South, you're far more likely to encounter L. mactans, the Southern Widow. And if you live in New England or Southeastern Canada, L. variolus--the Northern Widow--is your native species. And if you're Jerome a Paris? Well, the L. mactans tredecimguttatus--the Mediterranean Widow--is more in style, with a range that includes all of Southern Europe east into Kazakhstan.

So how is a budding arachnologist like yourself supposed to tell the difference? Well, if locality isn't enough for you, you can just go ahead and examine the red "hourglass" that make the "black widow" famous.

Black widows are known for their "hourglasses", but only one of the species mentioned above has a true hourglass marking--and that's the Western Widow, as you can see from the picture below:

The Southern Widow has a marking that actually more closely resembles an anvil shape:

And the Northern Widow actually has two separated red markings:

And the Mediterranean is quite visibly different, with spots (tredecimguttatus means "bearing 13 spots"!) all over the abdomen:

But that's not all! There are 31 different species in the Widow genus. I'll take up just a little more of your time and introduce you to a few that you've probably never seen before.

There are two other Widow species that you might see if you like in Central or South Florida. One of them is the L. bishopi, the Red Widow--and the only place you'll find L. bishopi is in palmetto fronds in Central and South Florida scrub-pine areas, which is too bad:

There is also another species in Florida, but it's nonnative, having been introduced there from other tropical ports of call. It's L. geometricus, the Brown (or Grey) Widow:

There are no recorded cases of Red Widow bites, but the venom is undoubtedly toxic. The Brown Widow has less dangerous venom, but should still be accorded respect.

Widow spiders are scattered throughout the world. If you're in Australia, you might find L. mactans hasselti, the Redback spider--and South Africa has six Widow species, including the intimidating L. indistinctus, whose distinctive red mark appears on the very tip of the abdomen.

But perhaps the largest debate among scientists today concerning the Widow genus is what to make of another potential American species, currently dubbed L. Bush:

L. Bush has been previously observed causing the death of potential mates, though this behavior has not yet been duplicated as a natural phenomenon, so no definite conclusions can be drawn. Other potential clues pointing to successful identification in the genus Latrodectus has been the tendency of this species to pair-bond with a non-threatening, easily controllable male, as well as the proclivity to retreat into a burrow and hide during times of danger. Nevertheless, the scientific evidence is inconclusive, and we are awaiting further study.

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