TOP ELEVEN PEST- BLACK WIDOW SPIDERS
These spiders get their common name from the popular belief that the female eats her mate after mating, something that rarely happens
in nature. The genus Latrodectus is worldwide in distribution, with 6 species found in the United States.
Identification:
The adult female has a body length of about ½" including an almost spherical abdomen of about 1/4-3/8" in diameter, with overall
length including legs of about 1 3/8-1 1/2", with males being about half the size of females. The color is typically black. The
underside of the abdomen is marked with 2 reddish triangular markings, usually joined to form a reddish hourglass shape, but
sometimes the markings are split.
The males usually have a color pattern on top that is variable but typically consists of a median row of red spots with white lines
radiating out to the sides.
Young spiders are primarily orange and white, but acquire more and more black as they mature, with marking similar to those of the
male, with 1 or 2 reddish markings on the underside of the abdomen.
Dangerous:
The female is the one with the poisonous venom. She is normally shy and retiring, but will become aggressive just after laying eggs,
and while guarding her eggs. The bite is usually the result of a defensive action by the spider. If you put yourself in a position
that threatens the spider you are likely to get bitten. The bite is not always felt, so the only reliable evidence of a bite is a
slight local swelling with 2 tiny red marks where the fangs entered. However, pain is almost always immediate >> back to top
and at it’s maximum within 1-3 hours. It continues for 12-48 hours, and then gradually subsides. The major symptoms are increased body temperature and blood pressure, profuse sweating, and nausea. If bitten, immediately call a physician or go to an emergency room, and take the spider along, if it can be SAFELY captured, for identification. There is an antitoxin available, and if treated, a bite is rarely fatal, except occasionally to small children.
Habits:
These spiders build an irregular web and hang upside-down. The web is used to ensnare pray. The female will avoid light by hiding in a crack or crevice during the day, and coming out at night to work her web.
Within a few days of hatching the spiderlings will climb to a high point with suitable air currents and spin a silken thread, and float on the breeze like a kite. This ballooning provides for the general distribution of the species.
Once they have landed they are usually found in protected locations such as under stones and pieces of wood, in firewood piles, under decks, in hollow stumps and trees, and sometimes in low tree branches and shrubbery. Some favorite places are manmade structures like barns, outhouses, henhouses, sheds, meter and water valve boxes, brick veneers, barrels and woodpiles. Indoors they are typically found in seldom used parts of the garage and basements, and in crawl spaces, preferring the more cluttered areas because they provide more harborage for their pray, which consists primarily of insects.
| Habits irregular webs in protected areas |
Biology takes a year to fully mature |
Dangerous when guarding and laying eggs |
Biology:
The female black widow deposits her eggs in a silken egg sac that is up to ½” in diameter. Depending on the species, a female can
produce from 6 to 21 egg sacks in her lifetime. Each sac can contain from 185-464 eggs on average, with a maximum found of 917.
Incubation is 8 to 30 days. It takes nearly a year for the spiderlings to grow to adulthood. After maturity a female can live from
800 to 950 days, and a male from 120 to 196 days, on average depending on species.
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