Posts Tagged: black widow spider
A sure-fire way to frighten arachnophobics is the very mention of "spiders"--especially on Halloween.
Spiders aren't insects but arthropods, order Araneae. They have eight legs, which according to some, are seven legs too many. They are also distinguished by their chelicerae with fangs that inject venom.
You've seen them. Black widow spiders. Jumping spiders. Crab spiders. Garden spiders.
If you fear them, there's a name for that fear: Arachnophobia. Wikipedia says that "People with arachnophobia tend to feel uneasy in any area they believe could harbor spiders or that has visible signs of their presence, such as webs. If arachnophobics see a spider, they may not enter the general vicinity until they have overcome the panic attack that is often associated with their phobia. Some people scream, cry, have trouble breathing, have excessive sweating or even heart trouble when they come in contact with an area near spiders or their webs. In some extreme cases, even a picture or a realistic drawing of a spider can also trigger fear."
The general fallacies, as listed by Rod Crawford, curator of arachnids:
- Spiders are insects.
- "Arachnid" is just a fancy name for spider.
- You can always tell a spider because it has eight legs.
- All spiders make webs.
- The orb web (round or "geometric" web) is a "normal" spider web.
- A "daddy-longlegs" is a kind of spider.
- Most spiders could not bite humans because their fangs are too small.
- Any spider species can be found anywhere.
- All spiders are male.
- Spiders are most numerous in late summer.
- You are never more than three feet from a spider.
- Spiders "suck the juices" of their prey, and do not literally eat it.
- Spiders don't stick to their own webs because their feet are oily.
Meanwhile, over at the Bohart Museum of Entomology at the University of California, Davis, plans are underway for an open house themed "Insect Myths." They will focus on spider myths, too.
The event, free and open to the public, is set for Sunday, Nov. 23 from 1 to 4 p.m. in Room 1124 of the Academic Surge Building on Crocker Lane, off LaRue Road. Directed by Lynn Kimsey, professor of entomology at UC Davis, the museum houses a global collection of nearly eight million specimens and is the home of the seventh largest insect collection in North America, and the California Insect Survey, a storehouse of the insect biodiversity. The museum is open to the public four days a week, Monday through Thursday (9 a.m. to noon and 1 to 5 p.m.) but it sponsors special weekend open houses as well.
The remaining schedule:
- Sunday, Nov. 23: “Insect Myths,” 1 to 4 p.m.
- Saturday, Dec. 20: “Insects and Art,” 1 to 4 p.m.
- Sunday, Jan. 11: “Parasitoid Palooza,” 1 to 4 p.m.
- Sunday, Feb. 8: “Biodiversity Museum Day,” noon to 4 p.m.
- Saturday, March 14: “Pollination Nation,” 1 to 4 p.m.
- Saturday, April 18: UC Davis Picnic Day, 10 a.m. to 3 p.m.
- Sunday, May 17: “Name That Bug! How About Bob?” 1 to 4 p.m.
- Saturday, July 18: “Moth Night,” 8 to 11 p.m.
When you attend the Bohart Museum open houses, you'll probably have the opportunity to hold and/or photograph "Rosie," a 24-year-old tarantula. It's one of the critters in the live "petting zoo," which also includes Madagascar hissing cockroaches, millipedes and walking sticks./h3>/span>
Jumping spider eyes the photographer. (Photo by Kathy Keatley Garvey)
Crab spider on sedum eyes a honey bee. (Photo by Kathy Keatley Garvey)
Garden spider captures a honey bee. (Photo by Kathy Keatley Garvey)
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)
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