Female black widows often exhibit various red markings on the dorsal or top side of the abdomen, commonly an “hourglass” shape. Adult male black widows are half the size of the females, and are usually gray or brown rather than black and red.

Not all adult black widows exhibit the red hourglass on the abdomen – Some may have a pair of red spots or have no marking at all.

The black widow is commonly found: Outdoors – woodpiles, under stones, in hollow stumps, and in rodent burrows, privies, sheds and garages. Indoors – undisturbed, cluttered areas in basements and crawl spaces.

In late spring, courtship and 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.