Adult female black widow spiders are a shiny black color with a red hourglass on the underside of the abdomen (there are beneficial lookalikes without the red hourglass).
Immature females have a pale brown to black body with a white to orangish banding; they get progressively more solid black as they molt toward adulthood.
Male black widows are about 1/3 of the size of females are pale brown with white markings, resembling immature females.
Black widows prefer preexisting holes in dark, undisturbed areas. They hide during the day and are in their cobwebs at night. Black widows are common around building foundations, rock and wood piles, outbuildings, water meter/irrigation boxes and around exterior lighting.