In the Garden:
Rocky Mountains
August, 2004
Regional Report

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Spiders not only snare bothersome insects, their webs are intricate art forms.

Along Came a Spider

Even though they are spooky and not a favorite of most gardeners, spiders are actually our allies in the landscape. They feed on living insects and help in protecting our garden plants. One of my favorites is the monkey face spider that spins a delicate fishing net to capture flies, moths, and mosquitoes.

Spiders in the garden are master predators, but they're often misunderstood and destroyed when we spray our gardens for pests. Unfortunately, spiders are not considered attractive like butterflies, but the helpful role they can play in our landscape is worth investigating.

Spider Basics
Spiders are not true insects but are classified as arthropods, a group that includes mites, ticks, scorpions, harvestmen, and several other less familiar creatures. While insects have six legs, spiders have eight legs, two distinct body regions (insects have three), and typically eight simple eyes.

For the sake of simplicity, spiders can be grouped into those that trap their prey by snaring victims with webs and those that hunt and actively chase down their prey. Hunting spiders are more aggressive and equipped to tackle a wider variety of insects. Trapping spiders prey on flying insects and smaller kinds that get entangled in webs, some of which are intricate forms of art.

Silken Webs
Spiders produce silk from glands in their abdomens, and it is released through finger-like organs called spinnerets. It has been estimated that this delicate silk is actually stronger than a steel wire of the same diameter. Some spiders can create different kinds of silk, each custom formulated for a specific reason. For example there is silk used for web construction, a silk net to keep paralyzed prey for later dining, or silk to be used as a dragline for travel. Many female spiders enclose their eggs in a silken case or egg sac that can be mistaken for an insect's cocoon.

One of the most fascinating uses of silk is in the behavior known as ballooning, a way of dispersal for young spiderlings. Tiny spiders crawl up to the top of some lofty object and begin to spin strands of silk into the wind. As an air current catches these strands, the spiderlings become airborne and move wherever the wind takes them.

Next time you come upon a spider, don't panic. These creatures are among a gardener's best allies. Spiders will feed on the bad guys including caterpillars, beetles, leafhoppers, aphids, and mites.

Poisonous Spiders
There are a couple of spiders that are dangerous to humans and pets. The black widow spider is common throughout the region and can found in undergrowth, under rocks and crawl spaces, in wood piles, garages, window wells, basements, and other protected, dark areas. The female is about 1-1/2 inches long, jet black with a red hourglass figure on the underside. Some specimens may have this reddish mark divided into smaller red spots.

The brown recluse spider is about a half-inch long, usually tan or buckskin in color, with long, dark brown legs and a violin-shaped dark mark behind the eyes. The base of the violin mark is on the head with the neck pointing toward the abdomen.

Avoid these two spiders as bites are painful and dangerous. Treatments for such spider bites should be referred to a physician.


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