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Hobo Spiders

- A common house spider in homes in the Northwest -

Summary: Hobo spider (also called aggressive house spider) is frequently encountered in and around homes in the northwestern US and Canada. Bites from this spider may become necrotic and slow to heal but the exact cause is not well known.

Jack DeAngelis, PhD
OSU Ext. Entomologist (ret.)

Hobo spider (Tegenaria agrestis)

Hobo spiders are medium size, tan to brown in color with a herringbone pattern on the upper surface of the abdomen (right). The hobo spider makes a flat, funnel-shaped web. Encounters between people and hobo spiders often occur in the fall of the year when male spiders leave their webs to go in search of females. At this time they are typical of other wandering spiders in that they can be found indoors.

Distribution of hobo spider in North America

Hobo spider has a limited but expanding distribution in Noth America (see map below). The spider occurs in the northwestern US and southwestern Canada. The states of Oregon, Washington, Idaho are nearly completely involved, and hobo spiders are also established in southern Alaska. The distribution is slowly expanding south and east. The spider also occurs in parts of Europe.

common names: funnel web spider, aggressive house spider
female hobo spider
Hobo spider (female) Body length (minus legs) about 1/2". Photo from Wikipedia, Lee Ostrom, family-protection.com.
 

Are hobo spiders really poisonous?

There is some debate about whether or not hobo spiders are in fact poisonous. Some studies have shown that hobo spider venom causes skin lesions while other studies failed to demonstrate toxicity in humans. It is interesting to note that in Europe, the original home of the North America population, this spider is not considered to be poisonous.

Until this issue is settled you may wish to treat hobo spider as if it is poisonous and avoid direct encounters. You can wear gloves while working in the garden and especially around woodpiles where this spider has constructed webs.

If you believe you have been bitten by a hobo spider try to capture it so that a proper identification can be made.

Should I spray for hobo spiders?

No. Spiders are very difficult to treat with conventional insecticides especially for homeowners because they move so readily from area to area. Plus, I believe it is unwise to apply most insecticides indoors where you are continuously exposed to these materials. A better approach is to use spider traps. Continue trapping until you no longer catch spiders.

But, if you feel you must apply insecticides indoors use one of the new plant oil (botanical) insecticides instead of the more toxic conventional insecticides. These insecticides pose much less risk and are just as effective.
Distribution of hobo spider in North America
Distribution of hobo spider in North America (from Wikipedia)

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Jack DeAngelis, Ph.D.

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