Black Widow Spider


Widows are large, distinctive spiders in the genus Latrodectus. Latrodectus mactans, the black widow, is found throughout the world in warmer regions, and is the commonest species throughout the United States. The brown widow, Latrodectus geometricus, which is found throughout the southeastern U.S., was recently introduced into California. Members of this genus are strongly sexually dimorphic – females are large and shiny black to brown, usually with a distinctive, although sometimes variable hour-glass shaped red mark on the underside of the abdomen. The legs are long and slender, tapering to a point at the end. Males are much smaller, and are brown, with light and dark striped markings. Males are rarely observed because of their small size and cryptic markings. They do not feed or bite, and have a short life expectancy as they are often eaten by the female after mating.

female black widow female black widow

Widow spiders are found nearly worldwide. They are widespread in the United States, although they are most commonly encountered in the warmer southern states.

Black and Brown Widow spiders are common in and around homes, garages, barns and other manmade structures in California. They build a tough, messy-looking three dimensional web in or behind objects in secluded and protected locations. During the summer months they may also commonly be found outside under shrubs, and other garden plants, or near porch lights. These spiders feed on large numbers of insects, particularly flies, and crickets, so they are valuable biological control agents of these pests. They do not particularly like feeding on cockroaches, but will do so when other insects are unavailable.

All Latrodectus spiders have painful and sometimes dangerous neurotoxic bites. In fact these are the only spiders in the United States that have a neurotoxic venom. The bites cause extreme physical discomfort and illness for several days to a week and can only be treated symptomatically. Common symptoms include pain in the vicinity of the bite, muscle aches, severe abdominal pain, vomiting, muscular cramping, sweating, fever and headache. Oddly, the bite location itself may go unnoticed. There is usually no swelling at the site of the bite, where a small necrotic lesion may form, which heals slowly over a period of weeks or months. Black Widow bites are rarely life threatening but may be particularly dangerous for small children or individuals with chronic health problems. There have been no deaths from the bite of this spider for decades. Black Widow bites can be dangerous for pets, and can be fatal to small dogs or cats.

Control is not necessary unless a Black Widow is in an area frequented by people, particularly children, or by pets. It is important to remember that these are very shy spiders and never bite unless physically threatened.