Most  black widow spiders are medium sized. Their bodies are about half an inch long with a shiny, black, global abdomen. You can identify them because they are marked with a bright red, yellow, or white spot. 
 

Both species of black widows spin irregular webs of very tough silk. All black widows locate their webs in protected areas, usually on or near the ground, in dark corners, but its rare that you will see them in human dwellings. The female Black widow spiders are nocturnal in habit and very timid when approached by humans. The males, which are a bit smaller than the females, often wonder around in search of females during the brief mating season. The female black widow is the only one who would bite humans, and only when disturbed. The spiders venom affects the nervous system 
 

The Black Widow spider is a very unique animal. I believe that the Fort Worth Zoo should give it more room to move around, besides that the spider looked in perfect conditions. 
 

When I first visited the Fort Worth Zoo I instantly fell in love with the Black Widow and since then I have always wanted to know more about this spider. The Black Widow is a very unique animal. The spider is very appealing to the eye because of the beautiful bright red spot on the abdomen which is the trade-mark of a Black Widow.

Goodnight, Marie L. THE ENCYCLOPEDIA AMERICANA INTERNATIONAL EDITION.
      Danbury, Connecticut: Grolier Incorporated, 1989. 
Pennak, Robert W. Collegiate Dictionary of Zoology. New York: The Ronald Press Company, 1990. 
Harley, John B., and Stephen A. Miller. Zoology- Fourth Edition. New York: McGraw-Hill,1999. 

Http://www.fortworthzoo.com.