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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
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