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Black Widow Spider Spells Danger
The female black widow spider stood guard.
She clutched her two teardrop-shaped egg sacs, suspended from the web she'd earlier woven on the lip of the swimming pool. She spent the day crawling up, over and around them. Two sacs, about 300 eggs inside each one.
Her future offspring. Proud Mama. Dangerous Mama.
Below, honey bees buzzed in the catmint (Nepeta), a white cabbage butterfly fluttered about, ladybugs snatched aphids, and a cellar spider (aka "daddy long-legs," Pholcus phalangioides) waited for the spiderlings to emerge to partake of an all-you-can-eat buffet. Sometimes that can be a four-week wait.
The female black widow spider is a force to be reckoned with--her bite is the most venomous of all spiders in North America. The neurotoxic venom can kill humans, but that rarely occurs. Statistics show the human mortality rate is less than 1 percent.
Not so with the insects and other arachnids she traps in her web. They blunder into the sticky web, get stuck, get bitten, and get eaten. While they're struggling in the web, she punctures them and sucks out their body fluid.
Not a pretty picture. But it is when it's a house fly or cockroach!
The female black widow spider (Latrodectus hesperus) is easy to distinguish. About half an inch long and shiny jet black, she's characterized by a red hourglass pattern on the underside of her bulbous abdomen. But don't bet on the pattern or coloring. Some black widows have a fragmented pattern, and some display no hourglass pattern or no red coloration at all.
You'll often find black widows in the garage, in woodpiles, rock piles, backyard clutter, in corners of sheds or playhouses, and sometimes inside your basement or elsewhere in your home. They spin an irregular, sticky silken web, conveniently located near their future prey.
This arachnid is named "black widow" because of the old wives' tale that she always kills her mate and consumes it after mating. Not true, scientists say. The mating ritual is not always violent.
However, it's when the female black widow is guarding her egg sacs that she's considered the most dangerous. When she bites humans, the bite itself can be painless or quite painful, but should always require medical attention.
That's because the venom is a powerful neurotoxin that causes muscles to contract. "This spider's bite is much feared because its venom is reported to be 15 times stronger than a rattlesnake's," according to a National Geographic post. "In humans, bites produce muscle aches, nausea, and a paralysis of the diaphragm that can make breathing difficult; however, contrary to popular belief, most people who are bitten suffer no serious damage—let alone death. But bites can be fatal—usually to small children, the elderly, or the infirm."
Be careful out there!
Female black widow spider guarding her egg sacs on the lip of a swimming pool. (Photo by Kathy Keatley Garvey)
Cellar spider (aka "daddy long-legs" Pholcus phalangioides) waits for the spiderlings to emerge. (Photo by Kathy Keatley Garvey)
Bottoms up: Female black widow guarding her egg sacs. (Photo by Kathy Keatley Garvey)
Black Widow!
The very presence of a black widow spider, shiny black with a globe-shaped abdomen, strikes fear in most people.
And not just on Halloween.
"Many spiders will bite when trapped but black widow spiders (Theridiidae: Latrodectus) are the most dangerous North American species," write Charley Eiseman and Noah Charney in their newly published book, Tracks and Sign of Insects and Other Invertebrates: A Guide to North American Species.
"Their strong venom can kill," agrees George C. McGavin in the Smithsonian Handbooks' Insects, Spiders and Other Terrestrial Arthropods, "but a fast-acting antivenom can be given by injection."
The black widow is a cobweb spider and "the females produce about 200 to 250 eggs, attached to the web in a sac," McGavin says.
So, where can you find black widow spiders? They're usually in more concealed places than the common house spider, which is "found in any dry structure, including houses, basements an barns, as well as under natural 'roofs' such as overhanging ledges," according to Eiseman and Charney.
And, Eiseman and Charney point out, the black widow spider webs are "composed of extremely strong, coarse threads"--unlike those of common house spiders.
McGavin says black widow spiders are commonly found in leaf litter, under stones and in and around buildings.
We sighted one under leaf litter recently at the Harry H. Laidlaw Jr. Honey Bee Research Facility at UC Davis. Its distinguishing mark: the reddish-orange hourglass on its stomach.
Then last week we spotted a black widow spider guarding her gumdrop-sized sac in a secluded area of a UC Davis parking garage.
She didn't pay attention to the "permit parking only" signs.
Black Widow Spider
Weight Lifting
