A worldwide community photographing and learning about wildlife
Based on the markings, this should be Micrathena gracilis.
http://galleries.northoftheridge.com/gal...
http://www.uark.edu/ua/arthmuse/spinorb....
http://bugguide.net/node/view/840822/bgi...
http://bugguide.net/node/view/827508/bgi...
http://bugguide.net/node/view/801817/bgi...
http://bugguide.net/node/view/142518/bgi...
http://bugguide.net/node/view/1996/bgima...