August 29, 2010 in City

Late summer brings spider ‘invasion’

Arachnid abundance really just natural life cycle
Sandi Doughton Seattle Times
 
Erika Schultz photo

Renton resident Shannon Bowley lets one of her spiders climb on her hand on Saturday in Seattle. Bowley overcame her fear of spiders by keeping them as pets.
(Full-size photo)

SEATTLE – To the casual nature watcher, it looks like a spider invasion is under way.

Suddenly, webs are everywhere: Under the porch light. Draped from the mailbox. Suspended like chandeliers from every shrub and tree.

But Shannon Bowley knows what’s really going on.

“I’ve been following them since they were tiny little spiderlings,” said the young Renton woman, who overcame her fear of spiders by keeping them as pets. “They’re getting bigger now.”

That’s right. The arachnid explosion that ripples across Western Washington in late summer and early fall is nothing more than the kids growing up.

Hatched out in early May, the ubiquitous species known as European cross spiders spend their early days out of sight of all but the most dogged spider-hunters. Their tiny webs are tucked deep in the bushes where they chow down on bugs – and grow. Now they’re reaching adulthood.

“They need more space for their webs, so they’re building in open places – where people run into them with their faces,” said Burke Museum spider specialist Rod Crawford, who’s learned to expect annual calls about the psuedo-population boom. “I’ve heard it every year for 30 years,” he said.

What is unusual this year is the staggered way the spiders seem to be coming of age.

“In my yard, a couple are already mature,” Crawford said. “There are also quite a few that are so small they probably have a month to go.”

The season’s weirdly fluctuating weather, with extended cool periods, is probably the reason, he suspects.

At the same time the region’s most obvious outdoor spider seems to be everywhere, its largest house spider is also at its most active. Males of Tegenaria gigantea, the giant house spider, are on the prowl. And some are as big as your hand.

“The ones people are seeing are males that have reached sexual maturity,” Crawford said. “They’ve started doing what sexually mature males the world over do: Cruise for chicks.”

The sight of lovelorn spiders wandering around the house in early fall helps fuel the mistaken belief that spiders sneak indoors when the weather turns cold. In reality, only a handful of species can live both inside and out, Crawford said. The vast majority are adapted to one niche or the other. Which means that transplanting indoor spiders outdoors is not a kindness.

The cross spider and the giant house spider are both imports – non-natives that have muscled in on local species. That may explain why their activity peaks at the driest time of the year, when the region’s native spiders lie low.

Serious spider collectors like Crawford and Bowley don’t even bother going into the field in late summer. Even winter is more hospitable for a greater number of species.

The perception that Northwest spiders are more numerous in late summer – based on a couple of eye-grabbing urban species – is among the more innocuous misconceptions Crawford attempts to debunk with his award-winning Spider Myths website (www.washington.edu/ burkemuseum/spidermyth).

More vexing is the persistent notion that spiders are dangerous to people.

Of the nearly 800 species found in Washington, the hobo spider is the only variety west of the Cascades considered “medically significant”: capable of inflicting harm on humans. But hobo spiders are increasingly rare – thanks to the giant house spiders who have crowded them out. There’s also debate over how toxic the hobo’s venom really is.

Horror stories and medical misdiagnoses notwithstanding, the brown recluse – which can pack a nasty bite – does not live here. An occasional individual might hitchhike to the Northwest in a moving van, but they won’t breed outside of their range in the central Midwest and South.

Crawford has worked with spiders for 30 years and only been nipped twice. Neither was any worse than a mosquito bite.

“Spiders have no reason to bite humans,” he said. “They are not bloodsuckers. They are not even aware of our existence.”

Still, arachnophobia is passed from generation to generation. Bites or lesions of unknown provenance are blamed on spiders. Most folks are more apt to squeal and squash when they encounter a spider indoors, rather than give thanks for its bug-eating prowess.

Bowley used to shudder when she saw a spider run across the floor. Then one day she sat down to really watch a spider going about its business.

“I decided at that point there probably wasn’t any real reason to be afraid of them,” she said.

Her first captive arachnid was a jumping spider, a type known for keen eyesight and hunting skill. “I used to think they were dirty little creatures,” she said. “But they’re just like cats – always grooming themselves.”

Today, she breeds her own spiders, nurturing them from egg sac to adulthood. She’s even conducting experiments to figure out the role of diet and genetics in a spider’s size.

“I wouldn’t say I have a relationship with them,” she said, lifting a giant house spider from his cage and smiling as he ran up and down her arm. But she does warm to her eight-legged charges and mourns when they die.

“Some are more timid and others are more bold,” she said. “They’re not just clones of each other.”


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