Pieridae, Coliadinae, Colias sp. and looks like being Colias eurytheme or Colias philodice. Looks quite worn and there are also different color morphs in females and males. I think it is not 100% possible to be on the safe side with only this picture.
http://bugguide.net/node/view/80402/bgpage
http://bugguide.net/node/view/12864/bgpage
http://bugguide.net/node/view/3248/bgpage
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