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Spiders of Oklahoma: Black Widow

August 12, 2013

Black Widow

The female black widow spider (Figure 3) is slightly larger than the brown recluse and is glossy black in color. It is globular in shape and never hairy. It has eight eyes arranged in two rows. The overall length of the female (legs extended) is about 1 1/2 inches and the male is much smaller, about 1 inch long. The male usually has three light streaks on his abdomen but is recognizable by knob-like appendages on the front of the head. The female has slim, glossy black legs, but the best recognition mark is a reddish hourglass-shaped spot on the underside of her globular abdomen. The female spider is the important one to recognize since the bite of the female can potentially result in serious medical problems.

Life Cycle
The female black widow is not aggressive unless she is confined or disturbed. She is more likely to bite when she is guarding an egg sac. The egg sac is grayish and papery in appearance. The eggs require 8 to 30 days to mature. Each egg sac contains from 25 to 900 eggs (300 to 400 common), and a female may construct 4 to 9 egg cases each summer; however, large numbers of spiders are not normally found because the population is curtailed by the cannibalism of the young. Thus, only 1 to 12 young normally survive from each egg case. Growth requires 2 to 3 months, during which the male molts 3 to 6 times and females 6 to 8 times. The older females usually die in summer or autumn after laying their eggs.

The female black widow normally hangs ‘belly’ upward and rarely leaves her web. She is frequently found near houses (under eaves); around trash cans and dumps or ash piles; under boxes, low growing shrubs, crates, stones, and wood piles; and outdoor restrooms. Black widows are also found in rodent burrows, underground water meter casings, and in gas meter housings. Cold and drought seemingly drive black widows into buildings.

Effects of the Bite
The black widow is generally considered the most venomous spider native to North America. The bite of the female injects a neurotoxic venom, which commonly gives rise to very severe symptoms. The bite itself is usually similar to a pin prick, but excruciating pain can begin within a few minutes and spreads from the point of the bite to arms, legs, chest, back, and abdomen. Within a few hours symptoms such as chills, vomiting, difficulty in respiration, profuse perspiration, delirium, partial paralysis, violent abdominal cramps, pains, and spasms may result. The pain can be so severe as to lead to frequent diagnosis as appendicitis, colic, or food poisoning. Reports indicate that mortality from black widow bites results in 1% or less of the cases, with very young or very old individuals at the greatest risk. More typically, recovery is complete in 1 to 5 days. In case of a bite the victim should consult a physician immediately.

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