Spiders have eight legs and two major body regions, the fused head and thorax. They have jaw-like structures called chelicerae, at the end of these are a claw-like fang with an opening that is used for injecting venom into its prey. Spinnerets used for spinning webs are located at the tip end of the abdomen.
Spiders are Beneficial!
Spiders are considered beneficial because they feed on insects. Their habitat varies. Some prefer moisture and can be found in basements & crawl spaces or other damp parts of a building. Others prefer warm dry places such as subfloor, air vents, upper corners of rooms or attics.Most spiders hide in cracks, darkened areas, or other retreats they build of silk.
Most Spiders Pose No Harm
Many species of spiders are common household pests, spinning webs in corners, under furniture, and over lamp shades while unsightly cause no real harm. Spiders inject venom to kill their prey and are considered beneficial because they feed on insects. However, most spiders in the Northwest pose very little danger to people.
Spiders of Northwest Oregon
There are three spiders that may be of concern in Northwest Oregon (European house spider, Hobo spider, and the Yellow sac spider) however they are usually found outside and away from people.
The Hobo spider and the European house spider look very similar, needing to be identified using a microscope. Most often these spiders stay hidden and retreat if encountered. An occasional encounter may occur if they are found hiding in shoes, clothing hanging in a garage or a pile of firewood, and are disturbed or trapped. In this possibility, they may bite.
Spider experts classify these species as “agelenid” or funnel web spiders. They are usually found in rock walls, gardens, along foundations, in crawl spaces, in garages, piles of discarded lumber or firewood and etc.Their prey is cockroaches, crickets, earwigs, silverfish, other spiders, pill bugs, various beetles, and an occasional fly. They can move quite fast ½ to 1 meter per second.
The Hobo Spider
The Hobo Spider has gained the reputation of being dangerous and aggressive; sometimes referred to as the “aggressive house spider”. This misconception is thought to originate because of its Latin scientific name “Tegenaria agrestis”.“Agrestis” has been thought to refer to “aggressive” however in Latin, it actually refers to “fields” where Hobo spiders can often be found.
A reaction to their bite may occur depending on the sensitivity of the person being bitten. It is thought a bite from this spider could cause a severe reaction. If you do need to see a doctor for a spider bite it is recommended that the spider is taken along for identification.
The Oregon Department of Agriculture has instructions on their website for sending a spider in for identification.
Yellow sac spiders
This spider is not known to spin a web and can be found under planters, firewood, rocks, and on plants in curled up leaves. They hide in white silken sacs near ceilings or corners. As with the hobo spider bite, it is thought bites from this spider may cause a reaction especially if sensitive. If necessary to see a physician take the spider along for identification.
Black Widow Spider
Black widow spiders are most common in southwestern and eastern Oregon and are rarely found in Northwest Oregon. Black widow spider bites may be more serious and need medical attention. Their venom is toxic to the nervous system.
The severity of a person’s reaction depends on the area of the body where the bite occurs, the person’s size and general sensitivity, the amount of venom injected and the depth of the bite. An anti-venom specific to the black widow is available to most physicians. Again this is not native to the Pacific Northwest as the climate is too cold for them here.
A black widow has a globular, shiny black abdomen with two reddish or yellowish triangles on the underside. These form an hourglass marking. Its size is from ¼ to ½ inches in diameter depending on if it is full of eggs. Males are much smaller and lighter colored with light streaks on their abdomens. The web of a black widow is an irregular mass of fibers with a small central area the spider retreats to while waiting for prey. Webs are frequently found under boards, stones, or seats of outdoor privies. Also along foundation slabs, behind shrubs and brick or wood siding close to ground level. This spider does not usually enter a residence.
Brown Recluse Spider
The Brown Recluse Spider is found in the southern, western and Midwestern United States only. It is a myth they are found in the Pacific Northwest, for more information on this See the article from the Burke Museum by Rod Crawford.
How to Reduce Spiders in Your Home
- Remove or knock down spider webs and egg sacks under eves of your home.
- Remove spider webs and egg sacs from around light fixtures.
- Spiders are attracted to the bugs around light fixtures.
- Make sure screens fit tightly in windows.
- Firewood piles and clutter around your yard are attractive to spiders, clean them up.
- Keep landscaping such as grass or other ground covers away from foundations.
- Inside, vacuum up spider webs.
- Seal cracks to prevent spiders from entering.
American Extermination Plus, Inc. includes a treatment for spiders with the Platinum and Silver Eagle Service. Often an abundance of spiders indicates there are additional pest issues. Spiders are a secondary pest and taking them away may cause other pest numbers to increase.
The best way we can help is to do a thorough inspection to determine if other pest infestations are present. We know spiders in your home are a concern and we may be able to help you reduce the sightings of them. We will do a thorough inspection of your crawl space and outside perimeter and give you our recommendations.
Call us today to schedule a complimentary inspection. We look forward to helping you solve your pest problems.