Garden Good Guys: Spiders

By Nanette Londeree, Marin Master Gardener 

As you take a walk around your yard or around your neighborhood at this time of year you cannot miss the amazing spider webs the arachnids are spinning as they get ready for the winter.  You may learn to understand and appreciate these garden good guys as you read the article below.

Do you cringe when you happen upon an eight-legged creature scurrying across your front porch?  If it’s a spider, you’re in good company. Fear of spiders, known as arachnophobia, is one of the most common phobias around. It may come from concern about being bitten by a deadly type or simply the idea of the “creepy, crawling” things and their reputation promulgated by myth and media. Before you stomp on or otherwise dispose of it, consider that most spiders are hugely beneficial critters, feeding on pest insects in the house and garden.   

Along with scorpions, mites and ticks, spiders are arachnids with four pairs of legs, two body regions, six or eight simple eyes and a pair of jaw-like structures that end in a hollow fang used to eject their venom. These voracious predators have a wide variety of prey, feasting on insects, other spiders and related arthropods. Located at the tip of the abdomen are small, fingerlike spinnerets that produce the material known as silk that they use to make their webs. In addition to trapping their meals, they also use silk to float through the air (ballooning), enclose their egg sacs and line burrows.  The silk they produce can be sticky, dry or stretchy depending on the type of spider, and is one of the strongest materials in the world.

Some interesting facts about spiders:

• All spiders are poisonous (it’s how they kill their prey), but most are either too small or their poison is too weak to harm humans.
• The jaws of most spiders are too small to bite humans.
• All spiders produce silk but not all spiders spin webs.
• The brown recluse spider does not live in California.
• In California, the only spider capable of causing serious injury is the black widow.
• Little Miss Muffet sitting on her tuffet?  She was a real person; her father, Dr. Mouffet, believed that spiders could heal when eaten.

There are more than 36 000 different named species of spiders in the world with 3,000 of them in North America. Some of the more common ones you’re likely to encounter in or outside the house include:

Cobweb spiders / house spiders (Theridiidae) – frequent inhabitants of dark corners hanging upside down in an irregular, sticky web. Often found in basements, abandoned buildings, and piles of wood. stone, or debris, their brown bodies are globular like widow spiders. 

Crab spiders (Thomisidae) - colorful spiders with a crablike appearance; they generally appear on blossoms where they blend with their background and pounce on visiting prey. 

Funnel weaver spiders (Agelenidae) - the most common spiders found in homes, particularly during late summer and early fall. They produce dense mats of silk in areas such as shrubs, thick grass, or corners of buildings. Often mistaken for the brown recluse, they have a darker brown color with black markings on the abdomen.

Jumping spiders (Salticidae) - compact, active, and usually colorful spiders that like window sills and ceilings; they stalk and pounce on unsuspecting flies and gnats.     

Orb weaving spiders (Araneidae) - very large - the black and yellow garden spider is a typical example; they construct huge, sticky, wheel-like webs during the night, across sidewalks, doorways, between garden plants and in other areas, to trap flying insects. 

Wolf spiders (Lycosidae) - big, dark, and somewhat hairy spiders that hunt by running down prey on the ground. They often wander into homes in the cool autumn.

As garden good guys, you don’t want to kill these helpers, though you may want to keep them out of the house. Try the mechanical approach – close up window and door openings that allow entry (including penetrations around water pipes, electrical lines and foundation cracks). Inspect firewood before bringing indoors, and keep woodpiles and other debris away from the house.  Remove webs with brooms and vacuum them up, or outdoors, use a high pressure hose. 

The one spider you do want to be aware of is the female black widow, with their shiny black bodies and distinctive red hourglass marking on their underside. Only large female black widows can injure people. They’re pretty common in stacked garden pots and other sheltered, dry, undisturbed areas.  If you are bitten by a black widow spider, remain calm and seek medical advice, or call the California Poison Control Center at 1-800-8-POISON.

So, if you do happen upon a spider or two 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.