The johnny darter attains a maximum length of about three inches. The "X" and "W" marks along the sides of the body are characteristic. Two dorsal fins are present, the first with spines and a black spot. The anal fin has one spine. The body is light brown or yellow on the back and upper sides. Brown bars are present along the sides. A black teardrop-shaped mark is present under the eye. The breeding male has a black head and black anal and pelvic fins.
The johnny darter lives near the bottom of creeks, rivers and lakes. It spawns in May. The female deposits as many as 1,100 eggs under rocks or other objects lying on the bottom. The eggs are laid and fertilized while the fish are upside down. The male guards the eggs. The johnny darter eats crustaceans and insects.