The biology of spiders (brief)

There are between 35,000 and 50,000 different species of spiders in the world. In our area there are probably a few hundred species comprising 30 families. These species are not easily differentiated by the naked eye or even under magnification. Spiders vary between species to an intricate extreme. For this reason, scientists have organized spiders into families based upon the identifying characteristics such as mouth-parts, eye arrangement (most spiders have eight eyes), and leg parts such as claws and hairs.

Less than 10% of Western Washington spiders are able to live both in and out of doors. Outdoor spiders are accustomed to abundant water and food as well as the extreme temperature differences. Inside spiders are used to the interior conditions. Any spider translocated from one environment to another will likely return to where it came from. Rod Crawford, the arachnologist at the University of Washington, said, "there are about 25 HOUSE-ONLY spider species in Seattle, the others being less common. In places out of the city and surrounded by forest, a common house spider is the native forest species Callobius severus," (quoted from an email correspondence with Rod Crawford). In your particular situation you will notice a more prevalent species in each place based upon your location and what spider has been able to flourish in that area.

Spiders tend to live in dark, damp and low-traffic areas of your structure. They tend to live in similar areas outside as well. Spiders are predators that feed on other insects and each other. Some spiders are hunters and will chase down their prey, others will make a nest and wait for their prey to come to them. The Wolf Spider is a common, local example of a hunting spider.

Dangerous Western Washington Spiders

Tegeneria Agrestis (Hobo Spider)
The Tegeneria Agrestis, or Hobo Spider, has a bite that is dangerous and can produce a nasty sore that lasts from three weeks to as long as two or more years, when the bite is in a fatty area. The bite can leave a permanent scar. If we had a magnified picture of this spider, we could see the eye pattern would look like the Tegeneria family. Other distinguishing traits of this spider are its funnel shaped web & the "V" pattern on its abdomen. Remember, not every funnel web you see near your house is a hobo spider web.

The Latrodectus Hesperus (Black Widow)
The Latrodectus Hesperus, or Black Widow spider, does occur in Western Washington. The Latrodectus hesperus is the only "widow" spider (one of six in the family Latrodectus) that exists in the Western United States. This spider is black with the famous, red "hourglass" on the underside of the abdomen. Its venom is reported to be 15 times stronger than the prairie rattlesnake. Its web silk is stronger than most other spiders. Its web is not a uniform, spiral web, it is sporadic and thick sometimes looking like a funnel web, although the Black Widow Spider is not a funnel web-making spider. One popular myth about this spider is that the female eats the male after mating. The local arachnologist corrects that by stating, "The only known Latrodectus species in which mate cannibalism in nature is the rule, not the exception, are in the Southern Hemisphere."

Loxoceles Reclusia (Brown Recluse)
Contrary to popular belief, the Loxoceles Reclusia, or Brown Recluse spider, has not established any population in Western Washington. The Brown Recluse has only been established as having a U.S. population in the South-central and Southeastern parts.

Control Measures

Controlling Spiders is a lot easier than identifying them. Spiders live in the dark, damp and low-traffic areas in and outside of your structure. They eat other insects as their primary food source. Based on these two fundamental spider lifestyle practices, to control the current spider population, we need to drastically reduce the general insect population in and on your structure, as well as make normal spider habitats uncomfortable for them.