Most spiders are venomous, but very few pose any danger to humans. In Virginia, only the black widow and brown recluse spiders can inflict severe bites requiring medical attention, and the bite of the yellow sac spider is sometimes painful but nearly always harmless. Most kinds of spiders in Virginia avoid contact with humans whenever possible and are an essential part of the food chain.

black widow on a pink flower
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Black widow on a pink flower

Black Widow Spiders

Black widow spider-2
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Black widow on a branch

The northern black widow spider (Latrodectus variolus) and southern black widow spider (Latrodectus mactans) are both common in Virginia. A shiny black color and a bright-red marking on the underside of the abdomen make a mature female black widow spider simple to identify. A male black widow and an immature female may have different coloration from a mature female, and, unlike a mature female, their venom poses no threat to humans.

Black widows spin tangled, uneven webs in dark, hidden spaces such as woodpiles, rock formations and other sheltered areas. They occasionally seek shelter in damp sheds and basements but are rare inside homes.

The bite of a mature female black widow causes red, swelled skin and severe pain in the vicinity of the bite; those symptoms can be joined by nausea, abdominal cramps and sweating that can last several days, according to a Virginia Cooperative Extension publication.

Brown Recluse Spiders

Spider web, close up, differential focus
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Spider web covered in dew

Sometimes called the violin spider for the fiddle-shaped marking that starts on its head and extends onto its midsection, the brown recluse spider (Loxosceles reclusa) is rare in Virginia but is most likely to be encountered in the southwestern tip of the state. The brown recluse is light brown, and the tell-tale fiddle marking that begins directly behind its eyes can be used to differentiate it from superficially similar spiders.

As its name suggests, the brown recluse usually stays hidden; it is sometimes discovered beneath boxes, behind furniture, in seldom-used drawers and between pieces of firewood.

Its bite is usually painless at first, and symptoms such as fever, joint pain, chills, nausea and weakness sometimes occur within 24 to 36 hours. In rare, severe cases, tissue damage can occur at the location of the bite, developing into a painful lesion that can take months to heal.

Yellow Sac Spiders

Yellow Crab Spider
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Yellow spider on yellow flowers

Two related species -- Cheiracanthium inclusum and Cheiracanthium mildei -- collectively known as yellow sac spiders, are often found in Virginia. The former is a native to the United States, and the latter was introduced from Europe. The two spiders are similar in appearance, with a 1/4- to 1/2-inch body, pale-yellow or brown coloration and a darker abdominal stripe that does not quite reach the rear.

Sometimes found in man-made structures as well as outdoor foliage, yellow sac spiders have gained a fearsome reputation that may not be quite deserved. Their venom can cause painful, red swelling in the affected area and occasionally leads to a blister that takes a few weeks to heal. The symptoms are similar to those of a brown recluse spider's bite but less severe and quicker to heal.

Many suspected brown recluse spider bites actually may be yellow sac spider bites, according to information in an article from the University of Nebraska-Lincoln Extension in Lancaster County.

Treatment for Spider Bites

pile of wood
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Work glove on a pile of chopped wood

Spider bites are uncommon and usually occur only when individuals mistakenly handle spiders, roll onto them or put on garments with spiders hidden inside. Death from spider bites is exceedingly rare, and severe symptoms from them are most common in people who are very young or elderly and people who have compromised immune systems. Certain individuals with heightened sensitivity to the venom, however, can develop severe reactions to bites from usually harmless spiders.

Virginia Cooperative Extension recommends that sensitive individuals bitten by any kind of spider seek medical treatment quickly, and it recommends the same to anyone who suspects he was bitten by a dangerous spider. Avoid coming into contact with dangerous spiders by always wearing gloves, a long-sleeved shirt and long pants when handling firewood or working outdoors, and always check clothes, shoes and gloves before wearing them.