widow spiders - Defense Centers for Public Health

There are five species of widow spiders found throughout North America: the southern black widow (Latrodectus mactans), the northern black widow (L. variolus), the brown widow (L. geometricus), the western black widow (L. hesperus), and the red widow (L. bishopi). Widow spiders are generally timid, but may bite humans if they or their webs are disturbed.

Widow Spiders


^{Southern black widow}	^{Northern black widow}	^{Brown widow}	^{Western black widow}	^{Red widow}

What do widow spiders look like?

In general, mature female widow spiders are about ½ inch in length, have a large, rounded abdomen, and long, slender legs. Female widow spiders have many color patterns (see photographs below):

Southern black widow: black body with a red hourglass mark on the underside of abdomen.
Northern black widow: black body with two red spots on the underside of abdomen.
Brown widow: light-brown body with orange-red marking on the underside of the abdomen, and banding on legs.
Western black widow: black body with red hourglass mark on the underside of abdomen.
Red widow: black body with distinctive bright red legs and orange-red half-moon marking on the underside of abdomen.

Males are about half the size of females, with a more elongated abdomen and long legs. Male widow spiders are small and can be difficult to differentiate from other house spiders. Male widow spiders are not venomous, so they are not medically important. Contact preventive medicine personnel for assistance with spider identification.

Where are widow spiders found?

Widow spiders are found on every continent with the exception of Antarctica. In the US, widow spiders can be identified by geographic location:

The southern black widow spider ranges as far north as New York, south to Florida, and west into Texas, Oklahoma, and Kansas. Southern black widow spiders are also found in California, and throughout the deserts of the American southwest.
The northern black widow is typically considered an "East Coast" spider and ranges from northern Florida to south-eastern Canada. They are most common in the northern portion of this range.
The brown widow spider was introduced to Florida and has since moved north through Georgia, and into South Carolina. They have also been officially recorded in California, Alabama, Mississippi, and Texas.
The western black widow spider ranges from west Texas, Oklahoma, and Kansas and westward through the pacific coast states to the adjacent Canadian provinces.
The red widow spider is found primarily in sand-pine scrub habitats of central and southeast Florida from Marion County to Martin County.

How dangerous are widow spiders to humans?

The bite of a widow spider produces pain at the bite site, which spreads to the chest, abdomen, or the entire body. Often, fangs leave two small, red marks on the skin. Widow spider bites seldom produce much swelling or skin damage at the bite site. If you suspect that you have been bitten by a widow spider, seek medical attention. If possible, safely contain the spider and bring it with you to the hospital for positive identification. Antivenom is available for bites of the southern black widow. Muscle and chest-pain or tightness are the most common reactions to widow spider venom. The pain may also spread to the abdomen, producing cramping and nausea. In severe cases, the toxin can cause breathing and speech difficulty, heart irregularities, and even death from suffocation.

How can I reduce my risk of getting bitten by a widow spider?

Widow spiders often hide in clothing, shoes, and storage areas, and bite in self-defense when people accidentally trap the spider against their skin. Therefore, if you live in an area where widow spiders are prevalent, inspect and shake out clothing and shoes before getting dressed. Wear gloves, a long sleeved shirt, long pants, and boots when working in areas where widow spiders may live.

Widow spiders build loose and irregular mesh-type webs to capture insects. Most widow spiders prefer to build their webs near the ground in dark, undisturbed areas, on plants, in loose stones, and in wood piles. Indoors, these spiders can be encountered in the corners of rooms, behind furniture, under desks, in garages, outbuildings, basements, and crawl spaces.

What can I do to get rid of widow spiders in and around my home?

Sanitation and exclusion can effectively reduce widow spider populations in and around structures. Avoidance and habitat modification techniques are more effective than applying pesticides. Preventive medicine personnel from the local military treatment facility can identify spiders and provide control recommendations for on-post residents.

Non-chemical, habitat modification approaches: Stop widow spiders from living near your home because they may move indoors. Remove debris, trash, lumber piles, leaf litter, rock piles, and thick ground covers or dense shrubbery to eliminate potential hiding places around the foundation and walls of the building. Stacked wood provides an ideal habitat for widow spiders so store firewood as far from buildings as possible. Seal cracks and crevices where spiders can come in, especially around windows, doors, and pipes. Install tight-fitting screens on attic and foundation vents. Vacuum cobwebs and spiders from around furniture, fixtures, ceiling corners, floors, and baseboards while indoors. Immediately remove the vacuum bag, seal it in another plastic bag, and throw away in an outdoor trash receptacle when finished.

Chemical control: Pesticide application should only be considered as a last resort. If living off-post, it is best to hire a professional pest control company. Always read and follow all directions for use as the label is the law when applying pesticides. In the short term, applying a pesticide may reduce spider numbers, but pesticide applications alone will not provide long-term control or prevent widow spider infestations.