Spiders - June 16, 1999
Jeff Schalau, County Director, Agent, Agriculture & Natural Resources
Arizona Cooperative Extension, Yavapai County
When we were children, Little Miss Muffet taught us all to be deathly afraid of spiders. To make matters worse, any time a person has a serious reaction to a bite of unknown origin, it is usually blamed on a spider. Yes, they can bite. On the positive side, they are voracious predators that consume a variety of insect pests in the home and garden. In this column, I'll see what I can do to improve the image of spiders.
Now for the spider anatomy lesson. Unlike insects, which have six legs and three body parts, spiders have eight legs and two body parts. The front body part is called the cephalothorax and the rear is called the abdomen. Most spider have eight simple eyes (as opposed to compound eyes) on the front of the cephalothorax. In addition to four pairs of legs, they have one pair of pedipalps or leg-like sensory organs. To the rear of the abdomen are spinnerets that produce the silk for making webs and egg sacs.
All spiders are predators: they eat insects, other spiders, and related arthropods. While some species spin webs to capture prey, others stalk prey on the ground or vegetation and pounce upon them. Web spinning spiders usually prey on beetles, bugs, flies, moths and leafhoppers. Ground dwelling spiders prey on crickets (many people don't realize that crickets are destructive household and garden pests), mites, and beetles.
Spiders are closely related to insects and just a susceptible to insecticides, but I don't recommend using them intentionally on spiders. A broom or vacuum cleaner is effective in controlling spiders in the home. Outdoors, they are usually barely noticeable. Wood piles, crawlspaces, and cellars are likely place to watch for black widows and they tend not to bit unless you touch them or disturb their web.
Spiders that use a web to hunt invest a significant amount of energy and materials in doing so. Orb weavers the spin classic web with concentric circles. They sit at the center of the web or hide near the edge and wait for prey to become entangled. Funnel weavers spin funnel shaped webs. They wait in the small portion of the funnel for their meal. When it senses vibrations, the spider runs outs, seizes its prey, and runs back into the funnel. Dwarf spiders are active in the day and spin tiny webs that catch mites and small insects in and around crop plants.
Most stalking spiders still have a permanent home, but forage at will in their territory. For instance, sac spiders spin a a silken tube where they hide during the day. They go out to stalk prey and return home with their meal. Kind of like Chinese take-out. Wolf spiders are ground stalking spiders, have camouflage coloring, and females carry their young around on their abdomen. Jumping spiders are active in the day and pounce on prey from distances many times their body length. Lynx spiders are active hunters with good vision and brightly colored bodies.
Daddy longlegs are closely related to spiders, but not true spiders. They prefer to be near water. I often find them in our bathroom and I presume they crawl through the hole in the screen. They do not bite humans nor do they spin webs.
The black widow and brown spider (brown recluse or violin spider) can cause painful injuries or systemic illness. However, they seldom, if ever are fatal to healthy adults. If you are bitten a spider and have a severe reaction, then seek medical attention immediately. Black widow spiders are easily identified and the University of Arizona Cooperative Extension office in Cottonwood can assist you with identification of brown spiders.
Whatever you do, do not randomly kill spiders in your yard and garden. They are helping you out. The University of Arizona Cooperative Extension has publications and information on insects and spiders. If you have other gardening questions, call the Master Gardener line in the Cottonwood office at 646-9113 or E-mail us at firstname.lastname@example.org and be sure to include your address and phone number.
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