Egg -- Eggs are incorporated into grayish, silken balls about 12 to 15 mm in diameter. These egg masses contain 200 to 900 eggs and are found in the spider's web.
Nymph -- Entirely white at first, nymphs develop through five to eight instars. As they develop, nymphs become more similar in appearance to adult males, though smaller.
Feeding Habits -- This spider feeds primarily on insects and other arthropods but, when disturbed, it may bite people or animals.
Damage -- The female black widow possesses a venom 15 times more potent than rattlesnake venom. The bite is like a pin prick but causes pain within a few minutes of the attack. The pain spreads rapidly to arms, legs, chest, back, and abdomen. Chills, vomiting, difficult respiration, profuse perspiration, delirium, partial paralysis, violent abdominal cramps and spasms may occur within a few hours of the bite. The victim usually recovers in 2 to 5 days; about 5% of all black widow attacks are fatal. The black widow, however, usually bites people only when its web is disturbed. Male black widows do not bite.
Life History -- The black widow spider overwinters as a young adult in buildings or in sheltered places outdoors. In late spring, after a prolonged courtship, mating occurs. Soon afterward the female kills her mate and begins laying eggs. The grayish silken ball of eggs is attached to an irregular, tangled web with a funnel-shaped exit. Each female constructs 5 to 15 egg balls, each of which contains 200 to 900 eggs.
Young spiders emerge from the ball in 10 to 30 days. They are cannibalistic at this stage. Only a few nymphs from each egg mass survive. They require 2 to 3 months to develop into adults. Older adults die the same summer or autumn after laying eggs. The new generation of adults survives through the winter.