Poisonous monsters sneaking in from dark recesses and sinking fangs into unsuspecting victims are among the many myths that surround spiders. Arachnophobia, the fear of spiders, affects many people, including some gardeners.
Spiders are not insects. They have two body regions instead of three and eight legs instead of six. There are thousands of different kinds of spiders, but only three in Utah are potentially dangerous. Different species of spiders prefer different environments. Indoor environments attract some to basements, crawlspaces or other damp areas. Some prefer dryer areas, including upper corners of rooms, attics or floor vents. Some spiders spin webs, others do not.Spiders, like many other living creatures, prefer to overwinter in warm areas. They invade homes, and in some cases reproduce there. Female spiders lay eggs in egg sacs or clusters after mating, and eggs hatch within a few weeks. Mating and egg laying occur throughout the year, depending on the species.
Although many readers will not willingly believe this, all spiders are beneficial. Spiders do not feed on household furnishings, stored food or garden produce. They eat other insects! They greatly assist in controlling insects that damage homes and crops.
There are only three potentially dangerous spiders in Utah. The black widow, the aggressive house spider and the brown recluse have poisonous bites. Black widows and the brown recluse are not aggressive, and bites are rare, although they can cause serious illness. Aggressive house spiders are more common but still do not pose a serious threat.
Black widows are common throughout Utah. They live indoors or outside, but prefer protected areas, including window wells, sprinkler turnoffs, basements or undisturbed areas. Most problems occur in new subdivisions as natural populations invade newly constructed homes. Female black widows are poisonous, but males are not. Females are about a half-inch long, jet black in color, with a red hourglass marking on the underside of the abdomen. The males are smaller, with brown marks on the abdomen.
Brown recluse spiders are rare. Dr. Jay B. Karren, Utah State University entomologist, says brown recluse spiders have never been confirmed in Utah. Suspected habitats include garages, basements and cellars. The spiders are about a half-inch in length and a tan or buckskin color. The brown recluse has long, dark brown legs and a violin-shaped dark mark immediately behind the eyes. The base of the violin is on the head, with the neck pointing toward the abdomen. The brown recluse is the only spider that has three pairs of eyes.
Aggressive house spiders are present in Utah, and the reports of brown recluse bites are possibly misidentified as caused by this spider. These spiders are tan colored and have long legs.
Tarantulas are occasionally seen in Utah and are sometimes present in large numbers. Although some tarantulas are large with a ferocious appearance, they are not harmful to humans.
Other common indoor spiders include the wolf spider. These are large, move rapidly and range in length from half an inch to 2 inches. Wolf spiders do not spin webs but roam at night hunting for food. Many people confuse wolf spiders with brown recluse spiders. They lack violin-shaped markings behind the head and are shy and run away when disturbed.
Araneus spiders, also known as catface spiders, monkey face spiders or humpback spiders, are found throughout the state. They are brown, range from a half to three-quarters of an inch in length and have a large abdomen. The back of the abdomen is often wrinkled in the form of a cat or monkey face. They spin orb-shaped webs in undisturbed garden areas, garages, basements or other areas. They are not poisonous and are beneficial because they consume a variety of insects.
To reduce spider problems, remove rocks, wood piles, old boards or other hiding places from around your home. Caulk cracks and crevices in the foundation and make sure screens and doors are tight. Throw away papers, boxes or other potential hiding places from basements, crawlspaces or other storage areas. Remove webs to discourage the pests. Catch the spiders and release them outdoors. Sprays are not recommended, as spiders are resistant to most insecticides and do not absorb them readily. If large numbers of spiders are present and causing problems, residual pesticides may be used. Household formulations of Dursban, Diazinon, Malathion or Baygon can be used. Outdoor garden formulations of these products should not be used inside because of odors and other possible problems.
In the unlikely event that you are bitten by a spider, the American Red Cross recommends the following:
1. Treat the site of the bite with an antiseptic to prevent infection.
2. Apply an ice pack to the site to reduce pain and swelling.
3. If a poisonous spider is suspected or if serious symptoms, such as increased pain or swelling develop, see a physician immediately. If possible, the spider should be captured and taken to a physician. Effective anti-venoms are available for black widows and certain other spiders. They can only be used if the spider that inflicted the bite is positively identified.