This is the most common harmful spider in California. The venom from its bite can cause reactions ranging from mild to painful and serious, but death is not likely. If medical treatment is obtained, many symptoms can be alleviated. Anyone bitten by this spider should remain calm and seek medical attention immediately; proper insect identification is helpful, so whenever possible the spider should be caught and saved.

The adult female black widow has a shiny black body, with slender black legs and a reddish hourglass on the underside of the large abdomen. The adult male Black Widow is about one half to two-thirds the length of the female, has a small abdomen and is seldom noticed. The male has venom as well, but its fangs are too small to break human skin.

The Black Widow has an irregular web that is very tough-stranded. The egg sacs are mostly spherical, about 1/2 inch long and 5/8 inch in diameter, creamy yellow to light tan in color. A female may produce several egg sacs, the tiny young Black Widows which are nearly white in color, disperse to new locations by ballooning and infest new areas.

The Black Widow are generally found in dark, dry, sheltered, relatively undisturbed places such as among piles of wood, rubbish, or stones. They also are found in garages, sheds, utility meter boxes, and crawl spaces. People are most likely to be bitten when they disturb the spider while they are cleaning out or picking up items in such places. Wearing long sleeve shirts and gloves could help to avoid any bites when working in these types of areas.

The symptoms of the Black Widow bite are largely internal. Pain tends to spread from the bite to other parts of the body and muscular spasms may develop. Other effects are fever, increased blood pressure, difficulty breathing, restlessness, nausea, and sweating. The symptoms reach a maximum at about a day, and they subside of the next 2 to 3 days. The Black Widow Spider is fairly common in California.

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