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Garden Spiders
Nature Bulletin No. 418-A   May 8, 1971
Forest Preserve District of Cook County
George W. Dunne, President
Roland F. Eisenbeis, Supt. of Conservation

GARDEN SPIDERS
Our handsome, bright colored Garden Spider or Orb Weavers are second in size only to the giant silk spiders of the tropics and are far better known. Their great webs, strung across garden paths or between shrubs and tall weeds in meadows, marshes and roadsides, are perhaps the most intricate and exquisite structures made by any of the lower animals. This delicate lacework is an engineering marvel with precise angles and spacing, as if the spider were able to measure and calculate stresses and strains.

The family of Orb Weavers includes about 120 known species; most of them in Australia and the Orient. Only a few kinds are found in the New World but, of these, three conspicuously marked species are widely distributed in both North and South America. They belong to a group called Argiope (which rhymes with "calliope"). The Silver Argiope, marked with metallic silver and yellow, is a common spider of the tropics and ranges through our southern states from Florida to California. The Banded Argiope, which has a rounded abdomen usually silvery white or yellowish and crossed by several dark lines, is abundant over most of the United States, especially in the West.

Our most common and familiar garden spider is the Orange Argiope or Orange Orb Weaver. Their strong symmetrical webs, often 6 or 8 feet across, are spun by large showy females. She has a plump body over an inch long, colored black with bright orange and yellow spots, and long velvety legs. The main framework of her web is built of supporting guy lines to which are attached threads radiating from the center like spokes of a wheel. These are rather stiff, inelastic, and not sticky. Then, around the center, she lays down a gradually enlarging spiral of beaded sticky silk for ensnaring insects. As a final touch, like the signature on a work of art, she spins a zigzag band of white silk down the center. On this she sits, head downward, waiting for a victim. When an insect, usually a grasshopper, hits the web, she runs out, rolls it in a blanket of fine silk, bites it to death, and then carries it to the center of the web where she sucks its juices at her leisure. If teased with a twig, she shakes the web until it becomes an indistinct blur, much like an enraged chimpanzee in a cage.

In autumn she encloses about a thousand tiny yellow eggs in a silken cocoon the size of a hickory nut and hangs it on a tall weed. The spiderlings hatch but remain in the cocoon -- feeding on each other ! -- until the following May when the survivors emerge to weave another year's orbs for your garden.

From the time the tiny spiderlings emerge from the cocoon, until they grow old and die, they are continually spinning silk -- often several kinds of it for different uses. The liquid silk flows from the glands in the abdomen, out through fingerlike spinnerets, and hardens quickly. Some glands produce the dragline -- made when a spider drops downward or runs over the ground -- and the main framework of the webs, which are not sticky. Other glands make sticky elastic threads such as those used to trap insects. The thinnest threads, only one- millionth of an inch thick, are invisible to our eyes. Others are stronger than steel.

Grecian mythology named the spider for the Lydian princess Arachne who challenged the goddess Athene to a weaving contest -- and lost. She was changed into a spider and condemned to spin forever. The male spider spins his own little web but is not much larger than a mosquito and weighs less than one percent as much as mamma.


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