Black Widow Spiders

General Description
Adult female widow spiders have bodies up to one-half of an inch long. Much smaller are the male black widows and immature females that are gray to brown with spots and stripes of red, orange and/or yellow on the upper surface of their abdomens. Thus not all widow spiders are black. But in the United States, adult females of the three most common widows are almost always a shiny black. The familiar “hourglass” marking located on the underside of the female’s bulb-shaped abdomen is bright red or red-orange. In northern black widows (Latrodectus variolus), the upper and lower halves of the hourglass are separated into two red spots, while the marking on the southern black widow (L. mactans) is represented by a single, red, hourglass-shaped mark. There is, however, considerable variation among individual widow spiders. Some have no hourglass markings. Most have a smaller red spot near the tip of the abdomen. There may be a line of red spots on the upper side of the abdomen, and northern widows often have white streaks on the sides of their abdomens.

General Control
Controlling black widow spiders also involves inspecting structures and outdoor areas for the presence of the spiders and their webs. This is best done at night because black widows hide during the day and hang in their webs at night. Like other cobweb spiders, black widows can be dispatched by vacuuming, if care is taken not to release the spiders when emptying the vacuum cleaner. Smashing them with fly swatters, boards and shoes will work as the spiders are not aggressive and cannot run away fast. Treating them directly with a contact pesticide is another option. Lastly, applications of residual pesticides, such as wettable powders or encapsulates, to crawlspaces and around foundations also can deter these and other types of spiders.