In this small clubtail, the thorax is mostly pale green in males and greenish yellow in female. The face and thorax are striped with black The length of the slender body varies from 1.2 to 1.4 inches. The black abdomen often has narrow rings. The legs are black.
Ranging through eastern United States and southeastern Canada, the least clubtail prefers wide gravelly, rocky riffles of warm or cold, clear streams. In Wisconsin, it is only known from a handful of northern counties.
Early June to mid-August in Wisconsin.