Spiders often are seen as ugly, threatening creatures. These eight legged, non-insect arthropods elicit fear and revulsion. Yet, they are a part of our every day world. They are viewed as beneficial when they capture insects but seen as pests when found inside the house.
Most buildings have a resident spider population feeding on household insects, stray flies, and each other. They live in neglected areas: attics, basements, behind and under furniture; bookcases or appliances; and in cracks between boards. Corners and baseboards are favorite locations.
Most house spiders are seldom seen except during housecleaning, but some of the larger species mature and become more active from late August to early October. At that time, the house may appear to have been invaded. Outdoor spiders do sometimes blow or crawl in through open windows, etc., but most either die of thirst in the house or fall prey to resident species.
Depending on your outlook, spiders in the house can be an advantage or disadvantage. A few spiders are rarely noticeable and help control other insects that find their way into the house. Spiders do, however, produce sheets or strands (cobwebs) of silk webbing, and small white specks of excrement which may drop on underlying items. People with allergies to spider venom, a fear of insects, or severe health problems should minimize the chance of any encounter with spiders.
Fear of Spiders
It is surprising how people have developed a fear of spiders. People who really aren't afraid may automatically behave as if they were. Horror movies, other people and just plain misinformation about spiders often are causes for this fear. Teasing by parents or children creates false impressions and fear. Another factor contributing to the fear is spiders move quickly, giving the impression they are "after" us. Other spiders hang around at eye level, where we blunder into their webs. People consider spiders to be ugly and frightening. In truth many are quite handsome or graceful, and all of them are fascinating.
Whatever the cause for fear of spiders, the fear is real. With some thought, effort and accurate knowledge about spiders, it may be possible to reduce the fear of spiders.
Spiders are predators of insects and other creatures. Usually they only capture prey smaller than or equal to their own size. Humans are far too big, even for the most ambitious spider. Many spiders are small and have small mouth parts. These spiders are not capable of biting through human skin.
Spiders which can bite through human skin only do so when provoked. Often bites occur when the spider is pinched or trapped in clothing. Their bite is merely a defense reaction; when you're cleaning the garage you may stick your finger in the spider's area, or trap it. Wearing gloves would prevent bites.
Lastly, humans out-weigh and out-size spiders many thousand times and are much more likely to behave with murderous intent. It should be the spider who feels "fear" at our approach -- not us. (Perhaps that's why they run so fast).
Spiders can be ignored if their numbers are small and they stay in out of the way places. They primarily eat insects already present in homes, such as cupboard pests, silverfish, or clothes moths. Sometimes they eat each other or capture stray insect invaders such as rootweevils and blowflies. Spiders that are more visible, like the ones that get trapped in the tub or run up a wall, can be captured and released outside, vacuumed up, swatted flat, or sprayed with an insecticide. (Do not over-spray).
Usually spider activity declines by mid-October. Unless you continually introduce new spiders on firewood, household spiders will retire into obscurity for another year, quietly killing several times their weight in household insect pests and flies.
Because spiders inject a small amount of venom into their prey, they are all "poisonous." Some spiders, however, are known to be dangerously venomous to humans. Their poison has a severe effect on most humans. Most other spiders, if they are able to penetrate the skin, produce only a mild reaction varying from none, to that of a mosquito bite or wasp sting, unless the individual has an allergy to that particular venom. Consult a physician if pain and discomfort follow a spider bite.
The only dangerously venomous spider known to occur in Washington is the western black widow, Latrodectus hesperus. There are only a few, small, permanent populations of this spider in Snohomish County, but it is quite common in eastern Washington. Specimens are sometimes introduced to the west side on vehicles and in hay shipments but generally cannot establish permanent populations in our climate. Widows are shy, retiring spiders and bite only reluctantly, usually only when molested. A common local house species, Steatoda sp., is often mistaken for a black widow but has no red mark.
The much feared brown recluse spider, Loxosceles reclusa is not known to be established anywhere west of the Rocky mountains. Occasional news reports of bites by brown recluse spiders have never been verified with an actual spider specimen.
More common in the Puget Sound Area is Tegenaria agrestis, sometimes called the aggressive house spider. This spider sometimes bites with little provocation when cornered or threatened. T. agrestis is more commonly known as the "hobo spider" as it is commonly found along railroad tracks. Hobo spiders can cause a severe reaction in persons allergic to spider venom, with the allergic reaction being very similar to that of the brown recluse.
As in all spider bites, if you can trap the offending spider, your County Extension Office should be able to tell if it is one of the dangerous species.
You alone can select the methods that will solve your spider problem or your reaction to the problem Fortunately, there will always be spiders. The best solution is to manipulate the environment so the spiders don't live where you do. It is unrealistic to expect that spiders can be totally eliminated. On the other hand, one need not live with abundant spiders. If you can't live with your spiders, some of the following approaches can reduce their numbers:
Intregrated Pest Management
Usually, successful pest management requires a combination or blend of methods. Each situation may require a different combination of management strategies.
The most reliable way to distinguish major spider groups is by arrangement of the eyes on the "head" region of the spider. On the large spiders, this eye arrangement is readily visible. A hand lens or magnifier may make the job easier in some cases.
1. Eyes in 3 rows, arranged in 4, 2,2 pattern (Wolf spider & Jumping spider)
2. Eyes in 2 rows of 4 (most spiders)
3. Eyes in 3 pairs (Brown recluse and relatives)
Using the eye arrangement is much more accurate when trying to identify Brown Recluse spiders and spiders which have been squashed.
The Hobo Spider Website
How to Identify (or misidentify) the Hobo Spider - PLS116 PDF file
The International Society of Arachnology
Spider Myths web site - U.W. Burke Museum
The Arachnology web site
Additional reading:Hobo Spider, a.k.a Aggressive House Spider by WSU entomologist, Todd Murray.
Spiders and Other Arachnids U.C. Riverside
WSU Publications Spiders, EB 1548: also available through your local WSU Extension Office for a nominal fee.
If you have additional questions contact your local WSU Extension office.