Super-Size Spiders Invade Local Gardens

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Written by Maria Gaura

Farm & Garden

SANTA CRUZ (November 2010) – For many Central Coast gardeners, fall is a season to avoid the back yard. We might blame our seasonal sloth on the waning daylight hours, or the lengthy to-do list of landscaping chores.
But I chalk it up the autumn invasion of garden spiders - those gangly, dangling web-hanging garden freaks that start out the size of your pinky fingernail and quickly balloon to Halloween-fright proportions. They seem to appear overnight, around mid-September, and enjoy flinging their nets across garden paths at face-height – a nasty surprise for the garden-variety arachnophobe.
And those webs are no mere gossamer – they boast sturdy lines that cling and stretch, then snap with a pling like an over-tightened banjo string. The sensation of having one of those babies wrap itself around your head is hard to shake, especially when it’s followed by the panicky thought, “is the spider in my hair???”  Then ensues what we call The Spider Dance, a frantic fandango of arm-flailing and hair-shaking, and maybe, sometimes, even a little shrieking.
While I am not fond of spiders, I like to think that I exercise great restraint in my dealings with them. I only squish the black widows, and employ the vacuum cleaner in extraordinary situations. Garden spiders, despite their off-putting habits, are nature’s very effective insect control, and a few weeks of tip-toeing through the yard waving a stick in front of me seems a reasonable trade-off for a healthy ecosystem, year-round.  
While our outsize arachnids seem to appear from nowhere, they actually live here year ‘round, according to spider expert Darrell Ubick, a curatorial assistant at the California Academy of Sciences in San Francisco.
“Do they really appear suddenly, or do people notice them suddenly?” Ubick said. “My feeling is the latter. At the end of summer the females get large and conspicuous, the vegetation begins to fall away, and the habitat opens up."
And as the females get bigger, they seem to climb higher and make larger, stronger, more prominent webs.
“This is the time that the females lay their eggs and guard the sac until the rain and cold comes and they die off,” Ubick said. “The eggs hatch in the winter, after the rain has saturated everything, and the spiderlings start their lifecycle. They’re out there all year.”
The stripey spiders now dangling in Santa Cruz area gardens are mostly orb weavers of the family Araneidae. California is host to a few dozen individual species of Araneidae, and the only sure way of positively identifying them is by examining their genitalia. “Seriously,” Ubick said, “That’s how its done.”
But generally speaking, Santa Cruz gardeners will find striking brown, orange and white striped orb weavers that string their webs at waist to face height, and spiders of the beautiful but sinister-looking black-and yellow striped Argiope family, which prefers to weave its webs somewhat closer to the ground. 
Despite their alarming size, garden spiders are considered harmless to humans. But it still makes sense to avoid them.
“They are venomous, as are all spiders, with very few exceptions,” Ubick said. “Spiders use venom to capture their food, and if you try to pick one up the wrong way - if you grab its abdomen - it will swivel around and bite. You risk a bite if you interfere with any organism, especially a female guarding its clutch - that is to be expected.”
Most humans tolerate a spider bite with little discomfort, but others can have painful or even severe reactions. That’s why I clear spider webs from high-traffic areas in the yard, and relocate pesky individuals over the fence with a long-handled broom. But spiders who claim out-of-the-way corners under the fruit trees, in perennial beds, or under the deck get to live in peace, and we watch in fascination as winter approaches and they assume ever more-bulbous proportions.
The larger they get, however, the more attractive they are to birds, and it’s not unusual in late October to find nothing but a ragged hole in the middle of a long-established web. A few weeks ago we had a dozen large spiders staking out our yard. But as of today, November 1st, only three remain.
Gardener who wonder in early October whether insecticide is needed to get rid of an abundance of spiders need only wait a few weeks for nature to bring the population under control.
“The system takes care of itself as long as we have diverse vegetation and critters and insects living out there,” Ubick said. “They maintain each other in balance.”