A long, slender, fast-moving lizard of open areas. Ground color is dark brown or black. There are usually six yellow stripes that extend from the head along the back and sides onto the tail. The stripes may be yellow, white, gray, or pale blue. The tail is long, tan, gray, or brown, with slightly spiny scales that are rough to the touch. The head and front part of the body are tinged with blue or green, especially in males. The belly is gray or bluish gray in males and salmon pink to creamy white in females. Racerunners can run across an open area at what seems like lightning speed.
Two subspecies in Missouri: The eastern six-lined racerunner (Aspidoscelis sexlineata sexlineata) is more common in eastern and southeastern sections. The prairie racerunner (A. sexlineata viridis) occurs statewide except for northern and north-central counties; it has 7 stripes instead of 6 and a wash of bright green over the head and front part of the body.