Spiders are nature's best pest control
Whether it's part of our DNA or learned behavior, most of us seem naturally afraid of spiders. Even those of us who don't tend to jump on chairs, scream or run from the first sight of the creepy-crawlies are more likely to instinctively kill them versus either capturing and moving them outside or simply just leaving them be. But very few species are harmful to humans.
And all spiders can be hugely beneficial in your garden or landscape. In fact, they are one of nature's best pest-control agents, feeding on insects, mites, snails and worms. Many people spend hundreds of dollars a month on pest control services that try to rid their properties of all spiders and insects. Not only is this usually unnecessary, but the chemicals used against the bad bugs also hit the good bugs and can kill thousands of beneficial microorganisms thriving in your soil.
Here's a rundown on the spiders you'll find in California:
Spiders you should befriend
• Funnel-web spiders, such as the common house spider (Tegenaria), build funnel-shaped webs in dark, moist areas. They sit at the mouth of the funnel and wait for their prey. Once an insect is tangled in the web they run out, bite the prey and carry it back into the funnel.
• Jumping spiders are compact, active and can be quite colorful -- even iridescent. They hunt during the day and often can be seen on window sills and ceilings where they stalk and pounce on unsuspecting flies and gnats. They can jump many times their body length; they do not spin webs.
• Orb weavers or garden spiders belong to the largest family of spiders. These spiders can be very large and therefore weave large, elaborate webs that are lethal to many kinds of flying insects: mosquitoes, moths, wasps, bees and hornets.
• Cellar spiders or daddy longlegs have long, skinny legs, as their name implies. They usually have grey/brown-patterned abdomens. They like to hang upside down in dark corners, often indoors, and weave irregular tangle-shaped webs.
• Sac spiders spin silk tubes under bark, among leaves, or in low plants or the ground. They use the tubes to hide in during the day and retreat to after hunting. The yellow sac spider is commonly found indoors on walls or ceilings, it is generally pale greenish-tan or straw-colored. Generally a bite from this spider will occur only when it has been trapped inside clothing. Usual symptoms include a stinging sensation similar to that of a bee sting.
Spiders you should beware of
There are two species of widow spiders in California, the western black widow (Latrodectus hesperus) and the brown widow (Latrodectus geometricus). Both have a similar body shape, reclusive habit and weave haphazardly constructed cobwebs.
A mature female western black widow is about a half-inch long (not including the legs) and shiny jet black with a red hourglass pattern on the underside of her rounded abdomen.
Juvenile black widows look nothing like their mother. As babies, they have tan legs, a tan cephalothorax and a white abdomen with a few black spots. As the juveniles grow, they become olive-gray with a longitudinal white stripe atop the abdomen and three diagonal stripes on the flank with black dots at the upper part of each stripe. Male black widows retain the coloration of the juveniles.
The brown widow spider has mottled coloration of tan, brown and gray. Its striped pattern is similar to the immature black widow, but is more tan than olive-gray. The hourglass on the brown widow is orangish in the middle with yellowish borders. The brown widow is not yet established in Santa Clara County but seems to be migrating northward from Southern California. Isolated specimens have been seen in Redding and Sacramento.
Widow spiders generally reside in cluttered area such as woodpiles, stacks of bricks and in garages. Brown widows may venture out to areas such as chain-link fences or exposed walls where black widows normally won't go.
The false black widow (Steatoda grossa) is not a true widow spider, but is of the same family. It has the same body form and rounded abdomen, but is slightly smaller and chocolate brown. It never has the red coloration on its belly.
Generally, only large female black widows can injure a human. If you are bitten by one, remain calm and seek medical advice. You can also call California's poison control center at 1-800-8-POISON.
Keeping spiders out
Even though I hope you are comfortable with spiders in your garden, if you can't live with them up close and personal, regular housecleaning should provide adequate control indoors. Be sure to vacuum up all cobwebs, and again, don't leave piles of clutter that provide them with great hiding spaces.
To prevent spiders from entering your home, seal all foundation cracks and access holes. Make sure window and door screens fit securely. Brush off cobwebs attached to the outside walls and eaves of your home and keep the outside perimeter free of clutter.
The University of California Integrated Pest Management website -- www.ipm.ucdavis.edu -- provides an amazing amount of great information on spiders, insects, diseases, weeds and much more. Be sure to check out the extremely helpful Pest Notes and Quick Tips; the photos are also amazing.
The Santa Clara County Master Gardener Program is a University of California Cooperative Extension volunteer organization that provides research-based gardening information to home gardeners. Master Gardener Lee Ann Ray and Mary Lou Flint, Director of IPM Education and Publications, UC-Davis, contributed to this column. Have a question for Rebecca Jepsen and the other Master Gardeners? Call the hot line, 408-282-3105, from 9:30 a.m. to 12:30 p.m. weekdays.
-- From Integrated Pest Management, UC-Davis, and Master Gardeners