Argiope aurantia

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Argiope aurantia

Kingdom:	Animalia
Phylum:	Arthropoda
Class:	Arachnida
Order:	Araneae
Family:	Araneidae
Genus:	Argiope
Species:	A. aurantia

Binomial name

Argiope aurantia
Lucas, 1833

Synonyms

Nephila vestita
Epeira aurantia
Epeira cophinaria
Epeira ambitoria
Epeira riparia
Epeira sutrix
Argiope riparia
Argiope personata
Argiope cophinaria
Argiope godmani
Miranda cophinaria

The spider species Argiope aurantia is commonly known as the Black and Yellow Garden Spider or Writing Spider. It is common to the lower 48 of the United States, southern Canada, Mexico, and Central America. They have distinctive yellow and black markings on their abdomens and a mostly white cephalothorax. Males range from 5 to 9 mm; females from 19 to 28 mm. Like other members of Argiope and almost all other spider species, they are considered harmless to humans.

1 Physical appearance
2 Habitat
3 Webs
4 Reproduction
5 References
6 External links

[edit] Physical appearance

This female of the species is striking in appearance with distinct yellow and black markings, including banding on the legs. Despite the vivid color, the garden spider is well camouflaged, blending in easily with partially sunlit areas. The female of the species grows much larger than the male. Females have large rounded bodies that may grow to 40 mm (1 1/2 inches), excluding the legs. If the length of the legs is added, the female can reach 75 mm (3") in diameter. Males are thin-bodied and only 20 mm (¾") long.

A. aurantia has three claws on each foot, unlike spiders that have only two claws and do not spin orb-webs. The third claw helps them manage the strands of silk while they spin the complicated web.

The young of the species resemble the adults, except for size and the development of reproductive organs. These spiders are not dangerous to people, and their bites result in nothing more than a sore, itchy swelling that goes away in a few days. The medical literature contains at least one report of a bite by A. aurantia (Gorham and Rheney 1968). Mild pain some distance from the site of the bite was suggestive of a neurotoxin.^{[citation needed]}

[edit] Habitat

Garden Spiders often build webs in areas adjacent to open sunny fields where they stay concealed and protected from the wind. The spider can also be found along the eaves of houses and outbuildings or in any tall vegetation where they can securely stretch a web. The circular part of the female web may reach two feet in diameter. Webs are built at elevations from two to eight feet off the ground.

[edit] Webs

The web of the yellow garden spider is distinctive: a circular shape up to 2 feet in diameter, with a dense zigzag of silk, known as a stabilimentum, in the center. The purpose of the stabilimentum is disputed. It is possible that it acts as camouflage for the spider lurking in the web's center, but it may also attract insect prey, or even warn birds of the presence of the otherwise difficult-to-see web. Only those spiders that are active during the day construct stabilimenta in their webs.

To construct the web, several radial lines are stretched among four or five anchor points that can be more than three feet apart. The radial lines meet at a central point. The spider makes a frame with several more radial lines and then fills the center with a spiral of silk, leaving a 5/16" to 3/8" gap between the spiral rings, starting with the innermost ring and moving outward in a clockwise motion. To ensure that the web is taut, the spider bends the radial lines slightly together while applying the silk spiral. The female's web is substantially larger than the male's, who builds a small zig-zag web nearby. The spider occupies the center of the web, usually hanging head-down, waiting for prey to become ensnared in the web. If disturbed by a possible predator, she may drop from the web and hide on the ground nearby. The web normally remains in one location for the entire summer, but spiders can change locations usually early in the season, perhaps to find better protection or better hunting.

Female A. aurantia

The Garden Spider can oscillate her web vigorously while she remains firmly attached in the center. This action might prevent predators like wasps and birds from drawing a good bead, and also to fully entangle an insect before it cuts itself loose.

In a daily ritual, the spider consumes the circular interior part of the web and then rebuilds it each morning with fresh new silk. The radial framework and anchoring lines are not usually replaced when the spider rebuilds the web. The spider may be recycling the chemicals used in web building. Additionally, the fine threads that she consumes appear to have tiny particles of what may be minuscule insects and organic matter that may contain nutrition.^{[citation needed]}

Female webs can exist as close as ten feet from each other, but there is usually more distance between webs. The Garden Spider does not live in dense clusters like other orb spiders such as the Golden Orb Web Spider. The Garden Spider keeps a clean orderly web in comparison to the cluttered series of webs built and abandoned by groups of Golden Orb Spiders.

[edit] Reproduction

Male A. aurantia

Yellow garden spiders breed once a year. The males roam in search of a female, building a small web near or actually in the female's web, then court the females by plucking strands on her web. Often, when the male approaches the female, he has a safety drop line ready, in case she attacks him. After mating, the male dies, and is sometimes then eaten by the female.

She lays her eggs at night on a sheet of silken material, then covers them with another layer of silk, then a protective brownish silk. She then uses her legs to form the sheet into a ball with an upturned neck. Egg sacs range from 5/8" to 1" in diameter. She often suspends the egg sac right on her web, near the center where she spends most of her time. Each spider produces from one to four sacs with perhaps over a thousand eggs inside each. She guards the eggs against predation as long as she is able. However, as the weather cools, she becomes more frail, and dies around the time of the first hard frost.

In the spring, the young spiders exit the sac and are so tiny that their collection of bodies look like dust gathered inside the silk mesh. Some of the spiderlings remain nearby, but others exude a strand of silk that gets caught by the breeze, carrying the spiderling to a more distant area.