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Marin IJ Articles

Creepy, crawly spiders help keep garden pests in check

  • Nanette Londeree
  • Spiders get a bad rap; many people go to great lengths to get rid of them.

    Is it their other-worldly appearance? Concern about being bitten by a poisonous type or simply the idea of “creepy, crawling” things? Whatever the reason, before eliminating them, it’s good to understand the invaluable role they play keeping pest populations in check.

    Found around the globe with at least 37,000 known species, spiders inhabit everywhere but the oceans and Antarctica. These eight-legged predators consume mostly insects and other spiders, injecting venom through their fangs to paralyze or kill their prey.

    Spiders you may encounter indoors are cellar spiders, cobweb spiders and funnel weaver spiders, while in the garden, you’re most likely to see crab spiders, jumping spiders, orb weavers and wolf spiders.

    Cellar spiders, also known as daddy long-legs, make irregular tangled webs in basements, storage sheds, ceilings and other dry locations with low light. Another creature often referred to as daddy long-legs is a harvestman, which is not a spider at all. This arachnid does have eight long skinny legs, but its body is one round segment and it doesn’t produce silk.

    Cobweb spiders are frequent inhabitants of dark corners in basements, abandoned buildings and piles of wood, hanging upside down in irregular, sticky webs. Their brown bodies are globular like widow spiders but they’re harmless (unless you’re an insect or spider). Funnel weavers are the most common spiders found in homes, particularly during late summer and early fall. The sit-and-wait predators produce dense mats of silk around cracks or recessed areas they use as a retreat.

    Colorful crab or flower spiders have enlarged front legs that give them a crab-like appearance. They hunt during the day and often appear on blossoms where they blend with their background and pounce on unsuspecting prey. Hairy-looking jumping spiders don’t build webs but stalk and swoop down on their target. They have excellent vision, the ability to jump impressive distances for their size and tremendous appetites.

    It’s hard to miss an orb weaver; the enormous mature females are adorned with exotic looking black and yellow markings. They spin elaborate webs in concentric circles in the garden and wait for prey to become entangled. With long, hairy legs, wolf spiders hunt by running down prey on the ground.

    The spider of greatest concern in our area is the black widow. Easily recognized, the mature female is shiny black with a distinctive red hourglass marking on her underside. These spiders seek out holes, crevices, trash and clutter, and are often found around homes, outbuildings and rock walls.

    Only large female black widows can injure people. Within an hour of being bitten, symptoms begin to appear that may include rigid stomach muscles, sweating and pain that can be local, radiating or regional, or simply resemble the flu. If bitten, seek medical attention immediately or call the California Poison Control Center at 1-800-8-POISON. Anti-venom for black widow bites is available and bite victims can go from intense pain back to normal in 30 minutes.

    The false black widow, harmless to humans, can be mistaken for its dangerous cousins; it’s slightly smaller, chocolate brown and does not have the red hourglass on the underside of the abdomen.

    A spider that gets a lot of press is the poisonous brown recluse.

    “No populations of brown recluse spiders are known to ever have resided in California,” according to Rick Vetter, Department of Entomology, University of California, Riverside. “We do have a healthy widespread population of a related species, the desert recluse, but it is found exclusively in the southeastern California deserts where not many people live.”

    If you happen upon spiders in the garden (other than the black widow), just ignore them and let them do their thing — helping to keep your garden pests in check.