   Respecting Spiders - January 5, 2005 Jeff Schalau, County Director, Agent, Agriculture & Natural Resources Arizona Cooperative Extension, Yavapai County Many people fear spiders because of myths, webs, fear of bites, etc. However, among scientists, spiders are usually considered beneficial because of their role as predators of insects and other arthropods. The truth is: most spiders cannot harm people. Spiders that might injure people--for example, black widows--generally spend most of their time hidden under furniture or boxes, or in woodpiles, corners, or crevices. Spiders commonly seen out in the open during the day are unlikely to bite people. Spiders are arthropods like insects, but they are classified as arachnids. They have eight legs and two body parts–a head region (cephalothorax) and an abdomen. They lack wings and antennae. Although spiders often are found on plants, they eat mainly insects, other spiders, and related arthropods, not plants. Most spiders have toxic venom, which they use to kill their prey. However, only those spiders whose venom typically causes a serious reaction in humans are called "poisonous" spiders. Spiders get into your homes in one of two ways: 1) because you brought them in (firewood, boxes, stored materials, etc.) or 2) because they are attracted to the prey insects living in and around your house and found a way in. You can prevent them from coming in by weather stripping doors, repairing screens, and caulking and control prey insect populations. Insecticidal treatments are not recommended for controlling spiders. Many types of spiders prefer living in houses and these species are generally not harmful to humans. Various kinds of small hunting spiders may wander indoors and occasionally, rather large, hunting-type spiders are discovered in homes or garages. Often these are fully grown wolf spider or tarantula males that have reached maturity and are searching for females. When these spiders are wandering, one or more may accidentally get indoors. New houses and other structures in developments may be invaded by wolf spiders that have lost their usual outdoor living places. The more insects there are inside a building, the more likely it is to have spiders living there. Usually spiders are most abundant in fall following the first few rains of the season. As stated earlier, most spiders cannot harm people. Of the thousands of species of spiders, only a handful are considered harmful to humans. In Arizona, the two most common venomous spiders are the black widow spider and Arizona brown spider (Loxosceles arizonica a relative of the brown recluse spider). Many people have seen adult female black widow spiders and can recognize them from their shiny black color and red hourglass pattern on the underside of their abdomen. Males and juveniles tend to show more color, with orange, red and white markings on the back and sides. Black widow spiders are shy and secretive and found in seldom-disturbed areas. The Arizona Brown spider is tan to brown and has a distinctive violin-shaped darker marking on the cephalothorax, with the neck of the violin pointed toward the abdomen. The eye pattern is also distinctive. Arizona brown spiders (and brown recluse spiders) have three pairs of eyes. Other spiders that might be mistaken for Arizona brown spiders have four pairs of eyes rather than three and do not have the violin pattern. When working in potentially spider-infested areas or handling firewood, always wear gloves and a long-sleeved shirt. When working in crawlspaces or attics wear a hooded sweatshirt and tuck your pants into your socks. If you suspect you have been bitten, try to safely capture the spider for identification (I know what you are thinking and yes, a smashed sample is better than nothing). Finding the spider is helpful in diagnosing and treating the bite and may aid physicians in diagnosis and treatment of spider bites (especially brown spider bites). Bites from blood-feeding insects (kissing bugs, bird bugs, and bedbugs) can be mistaken for spider bites. Learn to respect, tolerate, and enjoy spiders-they are excellent pest controllers in your garden and landscape. The University of Arizona Cooperative Extension has publications and information on venomous spiders and harmful insects. If you have other gardening questions, call the Master Gardener line in the Cottonwood office at 646-9113 ext. 14 or E-mail us at mgardener@verdeonline.com and be sure to include your address and phone number. Find past Backyard Gardener columns or submit column ideas at the Backyard Gardener web site: http://cals.arizona.edu/yavapai/anr/hort/byg/. |