The mature adult stage of Hexagenia limbata can be as much as 27 mm (1.1 in) long. The females tend to be slightly larger than the males but have smaller eyes. The forewings are long and membranous while the hind wings are much smaller and have dark margins. The tip of the abdomen bears two long cerci or tails. When the insect is at rest, the wings are folded vertically above the back. The color and body markings are somewhat variable but this insect is usually some shade of yellow, pale brown or white.