They are long and slender with a dark brown or black background and six yellow stripes. Their long tails are tan or gray with slightly spiny scales. Males have a wash of blue or gray on their throat and chest, especially during the breeding season. Racerunners are aptly named; they 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.