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Hobo Spiders
- A
common house spider in homes in northwestern US -
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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 of this injury is not yet known.
Jack
DeAngelis, PhD
OSU Ext.
Entomologist (ret.)
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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 North 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
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Hobo spider (female)
Body length (minus legs) about 1/2". Photo
from Wikipedia, Lee Ostrom,
family-protection.com.
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Are hobo spiders really venomous?
There is some debate about whether or
not hobo spiders are in fact venomous. 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 venomous.
Until this issue is settled you probably
should treat hobo spider as if it is venomous 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.
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Should I spray for hobo spiders?
No, not indoors. 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 hazardous 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 are trapping spiders on a regular basis.
Insecticide applied to the exterior
foundation below the siding ("perimeter spray"),
however, may prevent spiders from migrating into the
livings areas. Onslaught
Microencapsulated Insecticide (available here
from DoMyOwn.com, our affiliate) is approved for this
treatment but be sure
to check a current label for up to date usage
information.
If you feel you must apply insecticides
indoors consider using one of the new plant oil, botanical,
insecticides instead of the more toxic
conventional insecticides. These insecticides pose
much less risk and can be just as effective, see Using
Botanical Insecticides For Indoor Pest Control.
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Distribution (green) of hobo
spider in North America (from
Wikipedia).
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