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Thursday, October 28, 2004 - Page updated at 12:00 A.M.
Spiders: They really are superheroes
By Kathryn True
Imagine the earth a barren wasteland: defoliated trees, decimated crops, diseased livestock. It's not the results of a colossal drought or a head-on with a meteor, it's life without spiders.
Burke Museum-based spider specialist Rod Crawford is certain that spiders are more important to the proper functioning of the planet than we are. Without them, the insects that spiders constantly keep in check would devour and destroy plants and animals worldwide ending life as we know it.
Before rolling up this section of the newspaper to swat the gangly giant house spider scrabbling across your living-room floor, Crawford implores you to hear the one thing he wishes everyone knew about spiders: They pose little or no threat to humans. "They are all venomous, but the venom is not for us," assures Crawford, who has suffered only two insignificant spider bites in a 33-year history of handling and collecting tens of thousands of specimens.
Hariana Chilstrom, a naturalist at West Seattle's Camp Long who will lead a spider class on Saturday, agrees, "Spiders are not aggressive to people. Their first defense is to run, not fight, and they're running because they're scared of you!"
"The most toxic spiders in the world are nothing to worry about compared to a poorly trained pit bull or a nest full of yellow jackets, let alone a drunk driver," he said.
In addition to being nature's neat and clean insecticide, spiders are integral to a balanced ecosystem, and are essential food for baby birds, Chilstrom said. The bushtit also uses spider webs exclusively to piece together a hanging silken nest of lichen, leaves and animal fur. In the medical world, spider venom is being researched for use in treating victims of strokes and heart attacks.
Tools of the trade
Crawford chose Discovery Park because it's home to some species of grassland spiders found nowhere else in Seattle. However, a light but persistent rain made the forest a better collecting site, where he demonstrated how to use a beating net to gather specimens from trees. This same net can be used to beat low vegetation such as ferns and bushes and to sweep tall meadow grasses.
Holding the beating net underneath, Crawford used his hand to beat the lower branches of a young Douglas fir tree. Conifers yield more spiders than deciduous trees, and this combined with our abundant rainfall and varied habitats is why Washington boasts 860 different species, the most of any state. Anyone curious about spiders can use Crawford's scientific but simple methods to examine the diverse offerings in their neighborhood park or their own back yard a bed sheet can work as your first collecting net.
After circling the tree, Crawford carefully lifted up the sides and bottom of the cloth to view his finds. There was an exciting "treasure hunt" aura to this part of the process. Peering into the cloth sack, he named each of the creatures as they scurried to freedom. There was Philodromus rufus, with a striking reddish-brown body, and Theridion tinctum, a delicate beauty with extra long front legs, as well as several "micro-spiders," Crawford's term for those only 1 to 3 millimeters in length at adulthood.
He pointed out a harvestman. Often called daddy long-legs, these venomless spider relatives share the same class: Arachnida. Other accidental catches included insects such as European earwigs, adelgids (aphid kin), millipedes, centipedes and isopods. The sheer number of busy creatures extracted from these few branches was astounding.
Nice to meet you
Another simple and effective way to collect spiders is to use a sifting screen. Crawford uses a small plastic tub with its bottom cut out, lined with half-inch wire screen. He filled the container with bundles of leaf litter, then slowly shook it over a small sheet of light-colored canvas. A whole new collection of wriggling life fell to the cloth below.
"If you want to start a spider garden rule one is don't rake the leaves," Crawford said, explaining that moisture-seeking spiders revel in leaf mold, which protects them from their worst enemy, drying out.
Since most spider species are impossible to identify without a microscope and years of experience, distinguishing between different types of webs is a good place for beginners to focus. Orb, sheet, cob and funnel web weavers can be found at Discovery Park and throughout Seattle.
The thing to keep in mind this Halloween season: Spiders are not out to get you. And since there are from 100 to 200 spiders living in a typical house, why not get to know them a little better? Or "make a virtue of necessity," as Crawford likes to say.
"People have no idea how many insects they are being saved from," he says. With attributes more akin to benevolent Spider-Man than the spider monsters of sci-fi, these eight-legged houseguests are quietly protecting us as they go about the everyday process of procuring a meal.
Kathryn True of Vashon Island and Maria Dolan of Seattle are co-authors of "Nature in the City: Seattle" (The Mountaineers Books, 2003).
Copyright © 2004 The Seattle Times Company
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