Body may be up to 3/4-inch in length with the abdomen reaching 3/8-inch in diameter.
Typically glossy black but may also be dark brown to light brown. Related widow spiders may be brown.
The characteristic red markings on the underside of the abdomen often connect to form an hourglass shape, but this does not always occur. Some specimens may have red-to-orange spots on the top of the abdomen.
The black widow spider is widely feared because its bite results in severe pain that may take several days to subside. Such bites are rarely fatal but small children and elderly persons are at risk.
Black widow spiders construct irregular, scaffold-type webs usually near the ground level. These webs are almost always constructed in a protected site such as among items piled together, beneath boards, in firewood, and between boxes. Newly hatched spiderlings climb to high points, release a strand of webbing and are propelled by “ballooning” to new locations. For this reason, buildings may have new spiderlings float to it on a regular basis. Most of these do not survive. Black widows eat any insect they can capture. It is not true that the female always consumes her mate after mating, but it does frequently occur. Black widows are classified as dangerous spiders because their bite can cause severe cramping and pain throughout the body. Very young children, the elderly, and very ill persons are most at risk for severe reactions to the bite of this spider.
Bites most frequently occur when people are picking up an item under which the spider is hiding or putting on a shoe the spider has crawled into. Many bites are reported in outhouses where the black widow likes to spin her web below the toilet seat. (Be sure to check carefully before sitting down!) Black widows prefer to construct their webs in secluded, protected sites where insects are more likely to show up. Such sites are common in items stored haphazardly in garages or outside. Such clutter creates innumerable spaces suitable for spider harborage. Keeping boxes and objects stored neatly and away from walls is one step to minimize these spiders in or around a Home.
Bites can be avoided by wearing heavy gloves when moving items stored for long periods outside, in garages, in basements or in warehouses.