In common with other members of the genera Cloeon and Procloeon, C. dipterum has a single pair of wings.

[3] This is also reflected in the specific epithet dipterum, which is from the Latin di-, meaning two, and the Greek pteron, meaning wing, and in his original description, Carl Linnaeus stated Inferiores alæ vix existunt ("smaller wings hardly present").

[5] These extra eyes are thought to enable the males to locate isolated females in the mating swarm.

[2] Alongside new combinations of Linnaeus' original name in different genera (Ephemera, Chloeon, Cloe and Cloeopsis), true synonyms include three introduced by Otto Friedrich Müller in 1776 (E. annulatum, E. rufulum and E. dimidiatum), one by William Elford Leach in 1815 (C. pallidum), two by John Curtis in 1834 (C. marmoratum and C. obscurum), three by James Francis Stephens in 1835 (C. cognatum, C. consobrinum and C. virgo), and one each by Jules Pierre Rambur in 1842 (C. affinis), Costa in 1882 (C. apicalis), Bengtsson in 1940 (C. inscriptum) and Jacob in 1969 (C. szegedi).

[9] In 1953, a single female Cloeon dipterum was discovered in Illinois, having not been previously recorded in North America, and was found near Lucas, Ohio in 1960.