Thursday, September 2, 2010

Oh what a tangled web we weave

It was a lovely summer morning in the garden; a shimmering haze floating softly above the ground, the rising sun creating a warm glow in the midst of the mist.

In a nearby patch of overgrowth, stretched delicately among the Queen Anne’s lace and thistle was a gossamer web of enormous proportions.  Dew dangled elegantly from the silken strands, glistening like liquid diamonds.  Fluffy milkweed poofs trapped among the fibers of gauzy mesh.

And then I saw it.  Huge.  Bulbous.  Long, gangly legs stretching out from the yellow bespeckled abdomen.  Feed patiently from a vibrant green grasshopper which had the poor luck to become entangled and become this foul creature’s meal.  The web pulsing slowly, rhythmically with each draw of blood.

A spider.  A very very large spider.  Seriously . . .  I’ve never seen such a thing.  IT    WAS    COLOSSAL!

Okay, perhaps I may be over dramatizing.  This spider was truly quite big.
I tell you true . . . the arachnid was one big mama!

And a mama she was. 

The spider . . . a species of Argiope aurantia.  She is most commonly known, appropriately as the Black and Yellow Garden Spider.  She is also known as Writing Spider, Banana Spider or Corn Spider.  She inhabits a range from  southern Canada as far south as Mexico and Central America.

She has distinctive yellow and black markings on their abdomens and a mostly white cephalothorax (head). Males range from 5 to 9 mm (0.2-0.35"); females from 19 to 28 mm (0.75-1.1").  THIS MEASUREMENT DOES NOT INCLUDE THE LEGS.

As a reference . . . the size of US Quarter is 0.955" diameter

US Quarter

Thankfully, like other members of Argiope they are considered harmless to humans.

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 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.

Interestingly, the Garden Spider can oscillate her web vigorously while she remains firmly attached in the center. This is thought to 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. Only the center portion of the web is rebuilt, while the outer strands are left intact.

The male 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 will lay her eggs at night on a sheet of silky 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.

So there it is.  All you ever wanted to know about gigantic garden spiders.  

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