Heptageniidae

April to May

Korea and Russian Far East

The body and wings are around 12~18- and 10~18-millimeter-long respectively. Larvae are light brown, and the edge of the forehead is a little concave with a pair of light round patterns. The upper labrum is round and ectoderm of small mandible has a pectinate-shaped sting. The upper side of abdomen segment has bright patterns, tracheal gill of the first to seventh segments of the abdomen is white but unclear. They do not have filiform tracheal gill. They have three tails without any sting or chaeta.

Larvae inhabit in fresh valley water and feed on mosses (sphaerocarpus). Imagoes are observed very first in the valley early spring. They survive winter as larvae.