August 22, 2011

Charlotte's Webb

Recently, I came across this spectacular spider in the "knockout" roses. It is the spider species Argiope aurantia most commonly known as the Black and Yellow Garden Spider, Writing Spider, or Corn Spider which is a common orb spider. Orb web means it spins a web like a circle.

Female spiders are much larger than males,  growing almost an inch and a half long. Males grow about 3/4 inch long. The females have distinctive yellow and black markings on their abdomens and a mostly white cephalothorax.  Legs of these spiders are black with red or yellow bands. Each leg has three claws on the end. Like other members of Argiope they are considered harmless to humans. Because they are large, many people fear them; however, not only are they harmless, but they do a lot of good. These spiders eat large amounts of insect pests, such as flies, mosquitoes, and aphids.

These spiders prefer sunny places with little or no wind to built their webs. They 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 web may reach two feet in diameter. Webs are built at elevations two to eight feet off the ground.

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 the stabilimentum, in the center. The purpose of the stabilimentum is disputed. It is possible, it acts as camouflage for the spider, but it may also attract insect pray, 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. 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.

The garden spider hangs with her head down in the center of her web, waiting for prey to be caught. When an insect hits the web, the spider feels the vibrations and comes running. The spider can oscillate her web vigorously while she remains firmly attached in the center. This action serves to fully entangle an insect before it cuts itself loose.

In a nightly ritual, the spider consumes the circular interior part of the web and then rebuilds it each morning with fresh new silk.

Yellow garden spiders breed once a year. After mating the male dies, and is sometimes eaten by the female.

She lays her eggs on one side of the web, then covers it with a papery sac. The egg sac can be up to an inch wide. Over a thousand eggs may be inside. After laying the eggs, the female dies. The baby spiders hatch in the Fall, but they stay inside the sac through winter.

In the Spring, the young spiders leave the sac and go off on their own.  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.

A truly spectacular spider, I hope they see fit to grace my garden for many years to come.

1 comment:

The Sage Butterfly said...

I just saw one of these by my roses last week. It has such a lovely web. Great shots!