Spiders. The word itself is enough to send shivers up the spine,
but spiders are a beneficial and fascinating part of nature. And
thousands and thousands of them call the South Valley home, a few
of them harmful, but most of them not.
Spiders. The word itself is enough to send shivers up the spine, but spiders are a beneficial and fascinating part of nature. And thousands and thousands of them call the South Valley home, a few of them harmful, but most of them not.
Spiders have an amazing physiology. Except for jumping spiders, wolf spiders and a few others, most spiders are almost completely blind and sense their surroundings through vibrations, said Terrence Willett, director of research at Gavilan College.
Spiders also use the hair on their bodies to detect changes in air currents, and their webs – some with intricate designs and patterns – transmit vibrations to their feet, Willett said.
The geographical location of the South Valley brings cool air from the coast and warm air from the valley, creating ideal growing conditions for range grasses and alfalfas where many different spiders reside, said Christy Rachuy, an agricultural biology inspector for San Benito County.
Additionally, the abundance and timing of this year’s rain has attracted a variety of insects to the area, including spiders.
Some of the most common spiders in the area include yellow sac spiders, wolf spiders, wood louse spiders, garden orb weavers and – you knew it was coming – black widows, said Michelle Nachand, an agricultural biologist for Santa Clara County.
True to their name, yellow sac spiders range in color from yellow to light green and typically are about three-fourths of an inch in length.
The spiders can be found in the garden or inside the home and will bite if threatened, Nachand said. Human reaction to the bite varies but sometimes can leave a sore or hard, reddened area that can take several weeks to heal.
Turn up a rock in your garden and you may encounter the reddish wood louse spider.
Scientists don’t believe the wood louse is toxic to humans, but it does have large fangs and can bite if handled.
Garden orb weavers, native to California, camouflage themselves well outdoors, as they come in an array of shapes and colors.
Some have thorns that make it difficult for birds to prey on them, while others have unpleasant tastes.
“One type, the cyclosa, builds a pattern in a vertical line in the center of the web that is often littered with the bodies of previous kills,” Willett said.
More common to find in the home is the long-bodied cellar spider, Willett said. The spiders usually dwell in corners near ceilings and have long, thin legs.
They also have six eyes instead of the typical spider’s eight eyes, and despite their frail-looking appearance, the crawlers are adept at preying on several creatures including jumping spiders, ants and termites.
Long-bodied cellar spiders are not harmful to humans. The black widow and brown recluse, on the other hand, are two spiders in the area that can cause harm.
The black widow normally will run away if encountered, Nachand said, but a female might bite if she is guarding an egg sac or if she is cornered.
Black widows are especially common in basements, woodpiles and other cool, dark places.
They tend to stay in their webs and will bite only if provoked or caught by surprise. The bite usually isn’t serious but can seriously harm individuals who are allergic or whose immune systems are compromised.
A little more dangerous are brown recluses, small brown spiders with a violin pattern on their backs.
The spider’s venom travels through a person’s lymphatic system and can cause large ulcers of decaying flesh. It sounds bad, but don’t worry too much, Willett said.
“There are no confirmed established populations of the brown recluse west of Texas,” he said. “Though it may be that the occasional brown recluse may hitch a ride on a car or truck from that region.”
If you enjoy walking, biking or jogging on trails in the hills of Gilroy and Hollister, chances are you’ve noticed small black spiders out for a jaunt on the paths, as well.
“These are typically wolf spiders,” Willett said. “They are very different from the large, hair, tarantula-type spiders that are sometimes also called wolf spiders.”
Wolf spiders vary in size, shape and color, but all of them are hairy and have two large, forward-facing eyes, Nachand said. They are large enough to bite humans, but their bite is harmless unless the individual is allergic. The creatures usually are drawn to warm, open areas such as meadows and trails.
Burly spiders such as wolf spiders blend well with the natural landscape, but they’re not as picturesque when perched menacingly on a wall or ceiling inside your home.
One spider that might cause particular alarm indoors is the jumping spider, which Willett said has the best vision of all spiders. As implied by its name, the jumping spider hunts by chasing its prey and jumping from perch to perch.
To keep spiders from slipping into your home, make sure corners are well sealed and keep your house clean and free of piles of debris. Homeowners also can “de-web” their homes to rid them of spiders, especially areas such as cellars, closets, ductwork and registers.
In the garden, however, nature experts say gardeners would be wise to roll out the red carpet for the leggy creatures, which prey on other insects that can do damage to crops, such as aphids, mosquitoes and flies. Generally, spiders are attracted to a variety of colorful, flowering plants.
“Spiders tend to give most people the creeps, but they are really our allies,” Willett said. “Many farmers welcome spiders to eat pests and many artists are inspired by the intricate beauty of their webs. Take some time to watch a spider the next time you find one.”
