Our pest control technicians have been getting lots of complaints about spiders lately. A couple of customers have even stopped by our office, bringing dead spiders in Ziploc bags so we could identify the intruders. In both these cases, the culprits were identified as sac spiders by staff of our Sacramento pest control company.

Although the bite of the agrarian sac or yellow sac spider commonly found in our homes is not fatal to humans, this type of spider is believed to be responsible for more bites than any other spider, usually when trapped in ones clothes or bedding. The bite stings and causes a red welt and irritation similar to a mosquito bite. (If any insect bite causes a severe or unusual reaction, contact a physician immediately.)

The sac spider typically builds its sac-like web in corners, behind shelves and framed pictures and can sometimes be spotted running across walls or ceilings. It is light yellow with a darker stripe down the center of its upper abdomen and, like most spiders, has eight eyes arranged in two rows at the top of its head, difficult to see with the naked eye.

Most spiders are not dangerous and can usually be eliminated by removing their webs and/or eggs. Spiders seen out in the open during the day are unlikely to bite people.

Although we often hear reports of the brown recluse spider in our North-Central California region, in fact the brown recluse doesn’t live in California. The only recluse spider native to California lives in the Southern California desert and is less toxic to humans than its close relative, the non-native Chilean recluse spider, which has become established in Los Angeles County. Recluse spiders have a violin-shaped mark on their heads, which may or may not be easily distinguished, and have only six eyes. They are active at night and tend to stay hidden in dark, undisturbed places like storage boxes or old clothes or shoes.

The only California spider known to inflict serious injury to humans is the black widow, which usually is found outdoors in hidden locations such as in wood piles or underneath porches or sheds. Take care when you’re outside gardening, especially at this time of year, when the weather is still warm and sunny. The black widow’s web may not be visible in the sunlight, and you can easily stick your fingers into the wrong place.

The adult female black widow has a shiny black body, slender black legs, and a red or orange hourglass-shaped mark on the underside of a large, round abdomen. The body, excluding legs, is 5/16 to 5/8 inch long.

The best way to prevent spiders in your home is to vacuum up webs and avoid clutter build-up that can provide hiding places. To prevent spiders from entering your home or commercial building, seal foundation cracks and other access holes, keep window and door screens in good repair, and keep areas around the building foundation free of clutter.

For more information about identifying and controlling spiders and other household pests, visit our company's Website at http://www.earthguardpestcontrol.com. Additional information is available from the UC Statewide Integrated Pest Management Program. 

Dave Picton is owner of Sacramento pest control company, Earth Guard Pest Management Services.