Black widow: size: males 1/2", females up to 1 1/2". Mature females are jet black with two reddish triangular markings joined to form an hourglass shape on the center or underside of abdomen.  Males have whitish streaks, bars, or dots on their back with two triangular markings beneath. Immatures are orange and white and acquire more black in between successive molts as they mature. 
Nest sites: Typical outdoor habitats in which spiders are often found include wood and rock piles, rodent burrows, and hollow tree stumps. Indoor habitats include outhouses, garages, sheds, and basements. 
Black Widow