Geography 316: Biogeography
The Biogeography of the Writing Spider
By Charlotte Ely, student in Geography 316 Fall 2003
Thank you for visiting our site. This web page was written by a student in Geography 316: Biogeography and edited by the instructor, Barbara Holzman, PhD. All photos and maps are posted with specific copyright permission for the express use of education on these web pages. The students have tried to be as accurate as possible with the information provided and sources and references are cited at the end of each page.
Species Name: Argiope aurantia
Species: Argiope aurantia
|Figure 1: Argiope aurantia on web after rain. Photo by Jim Plank 2002|
Figure 2: Male approaching female. Photo by Michael Dietz, courtesy of Jim Plank
Both the male and the female have similarly striking features, though the male tends to be less colorful. The backside of the spider resembles a shiny little egg with bright yellow and orange markings that look as though a spider-loving psychologist, preparing a colorful inkblot test, splattered paint on a black surface. The spider’s “head” is covered in thin silvery hairs. Argiope aurantia’s legs are mostly black with red or yellow areas near the body; at the end of each leg, Argiope has three claws per each foot—they use this third claw to help handle silk threads while spinning webs (Milne and Milne 1980). The female of the species is much larger than the male—she can be up to 3 times his size. While female size ranges from about 19-28 mm, the typical male size ranges from about 5-9mm (see figure 2).
Argiope aurantia is found in the Neartic region of the world. One of eight ecozones, the Neartic consists of the terrestrial ecoregions of North America, including Greenland and the highlands of Mexico. Its distribution is largely continuous throughout the lower 48 states and southern Canada, though Argiope aurantia is not common in the Rocky Mountains or the Canadian Great Basin area (enature 2003).
|Figure 3: Map of United States-- Gray area indicates where Writing Spider is NOT found. (Library of Congress 2002)|
Argiope aurantia is a eurytopic species. Because it is such a generalist, the writing spider can be found throughout the temperate grasslands, prairie and scrublands of the North American continent. This common spider, sometimes called the black and yellow garden spider, is regularly found in backyards, much to the dismay of unsuspecting gardeners. Argiope aurantia prefers sunny areas among flowers, shrubs and tall plants. Open fields and meadows are another typical home for this sun-loving arachnid (Milne and Milne 1980). Likewise, the Writing Spider can also be found on weeds and tall grasses in marshes; Argiope aurantia enjoys open, sunny locations, long grass by the dunes or even a pretty flower by the driveway (see figure 4).
|Figure 4: “Zigzag” (the name given by the young photographer) in front of a driveway. Photo by Morgen Knott, courtesy of Jim Plank.|
Argiope aurantia (the yellow garden spider, the yellow and black garden spider, the black and yellow argiope, the golden orb weaver, yellow argiope, or the writing spider) is an orb-weaver. Orb weavers are famous, not only because of their debut in Charlotte’s Web, but because of the incredible webs they spin. E.B. White describes one of the webs in his cherished children’s story: “On foggy mornings, Charlotte's web was truly a thing of beauty. This morning each thin strand was decorated with dozens of tiny beads of water. The web glistened in the light and made a pattern of loveliness and mystery, like a delicate veil” (White 1952). Orb weavers are truly the artists of the Animal kingdom. Strands of silk are woven into intricate patterns; the “Writing Spider,” in particular, earned her name because she weaves a series of characteristic x’s through the center of her web, called stabilimenta (Castillo 1997). Spinning webs of the finest silks is no easy task. A typical web can take hours to construct and its beauty is fleeting: Argiope aurantia destroys, eats and then rebuilds her web every night (Moran 2003). A perfectionist? Maybe, but the Golden Orb weaver needs to be. The strength of the web is life; it must be able to hold prey thousands of time its weight.
Because spider’s silk is so durable and yet amazingly light, it has been the subject of great inquiry. In fact, Spider’s silk is the strongest, toughest fiber in the world—it’s even stronger and more flexible than steel. If produced in mass quantities, spider’s silk could be used “in applications where strength and lightness are essential, such as aircraft, racing vehicles and bullet-proof clothing…Another advantage of spider silk is that it is compatible with the human body…(it) could be used for strong, tough artificial tendons, ligaments and limbs. The new material could also be used to help tissue repair, wound healing and to create super-thin, biodegradable sutures for eye- or neurosurgery” (BBC 2000).
Some people have been utilizing spider’s silk for millennium:
“Polynesian fishermen use the thread of the golden orb web weaver…as fishing line. In the New-Hebrides, spider web was used to make nets for the transportation of arrow points, tobacco and dried poison for the arrow points. Some tribes in New-Guinea used webs as a hat to protect their head for the rain…
In 1709 a Frenchman, Bon de Saint-Hilaire, demonstrated (that he could) make fabric from silk. Many cocoons were boiled, washed and dried and the thread was collected with fine combs. Some socks and gloves were produced.
In Madagascar, there were some attempts to milk (orb weavers) for the production of silk. Thread was pulled (by hand) out of the spinner of the spider. If the spider was exhausted, she was put back in the forest and the next spider was milked” (Nieuwenhuys 2002).
Even the U.S. government was and is interested in using spider’s silk. The threads of Argiope aurantia and other orb weavers were used as hairs in measuring equipment during World War II (Nieuwenhuys 2002). However, because spiders are solitary and highly territorial creatures, producing silk in large quantities has been a trying task (i.e. spiders confined to crowded, small places kill and eat each other and if that isn’t economically inefficient…). The solution? Goats. In order to mass-produce spider’s silk, goats have been bred to harbor the silk protein in their milk—the “silk milk” is being produced in large quantities and has been dubbed BioSteel. Argiope aurantia may be one of the spiders being used to engineer “silk milk.”
Argiope aurantia’s web is not just remarkable because of its strength and beauty, but also in the way it reflects light. We all know that spiders weave webs to catch prey. We’ve all seen insects struggling in one or spun into a cocoon. We’ve all probably run into a web or two in our lifetimes. Spider webs are peculiar. Sometimes you see them; sometimes you don’t. It’s not necessarily because you’re too close or too far: it’s the angle, the quality of light—it’s that some spiders, Argiope aurantia, in particular, “produce catching silks that selectively reflect ultraviolet light.” In other words, parts of the web can be invisible to the human eye, but not to insects. Remember Argiope aurantia’s nickname: the writing spider. The name was extended because of the series of x’s it spins down the center of the web. “Argiope aurantia, has adapted a unique foraging strategy in which both UV-reflecting and non-UV-reflecting silks are spun on the same web. Argiope decorate their webs with UV-reflecting silk zigzags known as stabilimenta, while the rest of the web does not reflect UV light. The function of the UV-reflecting stabilimenta is to attract insects, using the same strategy the UV-reflecting designs on flowers (use to) attract pollinating insects” (Castillo 1997). In other words, those ‘x’s’ amount to a bull’s-eye so far as the insect is concerned and for the Writing Spider that means lunch.
The writing spider hunches and waits for its prey; she remains absolutely still in the center of the web with her head down and legs united in pairs. She doesn’t flinch, she doesn’t meander to and fro on that masterpiece of hers—she’s calm, cool and collected, ready for those recognizable vibrations that indicate: go. The following is a description by E.B. White:
Spiders, like Argiope aurantia, “drink blood” because they have no teeth. But, they’re not exactly drinking blood either and they do have fangs, but their fangs are not for chewing: “The mouthparts, called chelicerae, each end with a fang. The fang is connected to the venom gland, which enables the spider to inject venom into its prey…Spiders bite their prey and inject venom, which immobilizes the prey and starts the process of digestion. Spiders have no teeth and rely on the venom to liquefy their prey in order that their stomachs, known as sucking stomachs, can draw in the meal” (Lizotte 2002).
Argiope is no different from many other spiders in this regard, nor is she different in that she often eats her mate after they’ve copulated. However, Argiope aurantia is utterly unique in that she is the only known spider—known species on the planet— whose mate dies spontaneously during intercourse.
“Wham, Bam, Now I'll Die, Ma'am” by Silvia Sanides describes the practice:
“The orb-weaving male has two sperm-containing pedipalps that it inserts into the female. Upon insertion of the second palp, they invariably undergo a kind of programmed organismic death…The heart rate slows, and 15 minutes later the male is dead” (Sanides 2003).
The male’s death is also described as an “irreversible seizure” and apparently this takes place to form a kind of “chastity belt” (James 2003). Once the male Kamikaze has inserted the second palp, he’s stuck, despite what the surrounding males would like. "The other males go berserk, bite into the legs and try to pull him off." Securing himself inside of her not only prevents the future cannibaless from mating with another spider, but also gives the male’s sperm sufficient time to fertilize the eggs.
However, the female of the species does appreciate his sacrifice. After he’s dead, she gently wraps him in a body bag of silk and saves him for an afternoon snack (Sanides 2003).
Before he gets gobbled up, the male spends some time on the outer edges of the female’s web; he builds a smaller web and can wait days for her to receive him. When she’s ready for him, he’ll wave his legs about and “dance” to impress her. However before he begins with his first and final performance, he’ll deposit a bit of sperm on to a scrap of silk and then suck it into his “plunger-like palp” (Conrad 2003). It’s likely he does this to alert the female that he’s not only ready, but not lunch.
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