Spider Bites - Hobo, Widow &
Most spiders are harmless, a very few are venomous,
all are beneficial predators -
While most spiders are harmless and even beneficial,
a few have a venomous bite. In the US the most
commonly encountered venomous species are widow
spiders, brown recluse spiders
(south-central states) and hobo spiders in
the northwest. Learn how to recognize and avoid
spiders are harmless." No matter how often
this is repeated many people's innate fear causes
them to recoil at the sight of even small spiders. Most
spiders are harmless! Having repeated that,
however, there are a few that deserve to be
taken seriously and their bites should be avoided.
spiders are predators and all use venom to
subdue their prey. A few have venom in their bites
that is dangerous to humans. The venomous species
vary depending on where you live.
has an especially venomous species called the Sidney funnel web spider and
the tropics have a number of venomous ones as well.
In the US three spiders cause concern -- hobo
spider (aka aggressive house spider), widow
spiders and the brown recluse spider.
This page will help you identify and rationally deal
with these spiders.
spider venoms cause different types of injury. Some
cause necrotic, or "tissue killing", wounds
from so called hemolytic venom. These wounds
are very slow to heal and can become seriously
infected. Some spider venoms attack nerve tissue
with neurotoxic venom. These bites can lead
to trembling, convulsions, respiratory failure and
Black widow spider -
note red "hourglass" on underside of
abdomen. This is one of the highly venomous
Three related spiders commonly enter
homes. The house spider (Tegenaria
domestica), the giant house spider (Tegenaria
duellica) and the hobo spider (Tegenaria
agrestis). These species are very difficult to
tell apart except for fully grown, female giant
house spiders which are considerably larger than the
other two. Of the three only the hobo spider is
thought to have a dangerous bite and even these
reports may be exaggerated.
The house spider (T. domestica)
is found throughout North America while the giant
house spider (T. duellica) is found mainly in
the Pacific Northwest and western Canada. The hobo
spider (T. agrestis) is currently
expanding its range from the Pacific Northwest, east
and south (see What Do
Hobo Spiders Look Like? and Related
There are many reports of serious,
localized necrotic wounds resulting from the bites of
the hobo spider. Some researchers, however, doubt that
this spider is venomous at all. While the scientific
"jury" may still be out, care should be taken with
this common spider where it occurs. Use the
suggestions below for reducing the chances of bites.
Especially take care when working around woodpiles and
bringing firewood indoors. Encounters with all house
spiders are far more common during fall when
amorous male spiders are wandering in search of female
spiders. During the rest of the year these spiders
tend to be fairly secretive. All three house spiders
originated in Europe where, interestingly, the hobo
spider is not considered to be venomous.
Widow spiders (Latrodectus spp.)
spiders (see pictures) are very secretive.
They occur in undisturbed areas and under debris.
They rarely bite but bites can be very dangerous.
They possess a neurotoxic venom that can
result in serious medical complications, even death.
Fortunately anti-venom is now widely available. As
with hobo spiders be cautious when working around
woodpiles or undisturbed debris in areas where widow
spiders occur. Widow spiders tend to be more common
in dry and warm climates but occur throughout North
recluse spider (Loxosceles reclusa)
distribution of the brown recluse spider is
much more limited than many people believe (see range
map). It occurs only in the south-central US.
Bites sometimes result in serious necrotic wounds
that can develop into dangerous medical conditions
especially in individuals with a compromised immune
system. Brown recluse spiders often have a
distinctive "violin" shape mark on the spider's
upper surface (see What
Recluse Spiders Look Like?).
Treating household spider
Spiders that you find outdoors
can be left alone. They do not generally pose a
threat as long as you exercise some reasonable
caution. Wear work gloves when working around
woodpiles or debris piles. Widow spiders tend to
occur in out-of-the-way places in outbuildings and
crawlspaces so be cautious there as well. Sticky
board traps are usually the best solution for
spiders that wander indoors like male hobo
and recluse spiders (see Using
Spider Traps For Indoor Spider Infestations).
Widow spiders, on the other
hand, almost never enter living spaces.
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