Black Widow Spiders




Photographer: Ronald F. Billings, Texas Forest Service
Black Widow Spiders Latrodectus mactans (Fabricius)
Northern Widow Spider Latrodectus variolus (Walckenaer)
Spring and summer is when you find an over abundance of spiders around the house. In many instances, at least one of these spiders can be identified as the black widow . The black widow spider is present in every state in the union and is found in Canada and South America. The males and females are distinctly different in appearance. The female is shiny black with a bright red hourglass shaped marking on the underside of the abdomen. A mature female, with legs extended, is up to two inches long with the abdomen ranging from 1/4 to 1/2 inch in diameter. The male is much smaller with its overall length less than one inch. It is usually lighter than the female in overall color and has light streaks on his abdomen. The web on this species is also distinctive. The strands of silk run in many directions so the web appears as a concentration of irregularly arranged threads. The silk strand of the web is considerably heavier and stronger than those of other species that form similarly shaped webs. The female hangs upside down in the web such that the red hourglass faces up. The egg sacs, which contain up to several hundred eggs, are most frequently encountered from May to October. The female typically stays with and guards the sac until the eggs hatch. The young spiderlings remain inside the sac for several days subsequent to hatching. Within a few days after emergence, the spiderlings release strands of silk out into the breeze and are carried off into a new territory. Most of these flights occur during the early fall months. Development from egg to adult may take from two to four months or more. A female may live a year or more after maturity. Males are sometimes killed by the female soon after mating, thus the name "widow" is attached to the spider


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