From the U.S. Fish and Wildlife Service's online digital media library.
Check http://images.fws.gov/ for higher quality version, and http://www.fws.gov/help/policies.html for copyright information.

Metadata
Title: Bullsnake
Alternative Title: Pituophis catenifer sayi
Creator: U.S. Fish and Wildlife Service
Publisher: U.S. Fish and Wildlife Service
Contributor: DIVISION OF PUBLIC AFFAIRS
Language: EN - ENGLISH
Rights: (public domain)
Audience: (general)
Subject: species, reptile, snake, snakes, bull snake
Date Issued: March 17 2005