The side scales are also tipped with brown or black. This often gives the bullsnake a speckled appearance on the sides. The head is yellow or brown and boldly marked with black, including a stripe across the top of the head from eye to eye, barring on the labial scales, and a stripe from the eye to the corner of the mouth. The belly is porcelain white on the throat and fore part of the belly becoming yellowish with brown squares or spots thereafter. This snake has an enlarged rostral scale, keeled scales and a single anal plate.
Confusing species are the prairie kingsnake and especially the fox snake.
Prairie kingsnakes are brown overall and have smooth scales. Fox snakes are brown or yellow overall with no pronounced color change or speckling on the sides, a rounded snout, and a divided anal plate. The bullsnake is a subspecies of the gopher snake, Pituophis catenifer, which contains about six subspecies, occurring west of the bullsnakes range. The range of the bullsnake is huge, and it is found from Canada south to Texas and east to Illinois and west to Colorado. In Iowa, the bullsnake is found statewide.