Mayfly Species Procloeon intermediale (Tiny Sulphur Duns)

Abdominal tergites 2-6 of male imago pale whitish, hyaline; a geminate ruddy dorsal line ; posterior margins broadly ruddy.

Turbinate eyes of dried specimen bright red. Thorax deep brown. Posterior portion of mesonotum, and the antero-lateral margin, with ruddy shading. Pleura brown, shaded with ruddy at base of wing and on the intersegmental areas. Sternum light sepia brown, the intersegmental membrane pale yellowish. Legs pale yellowish; femora show very faint traces of ruddy median bands. Wings hyaline, venation pale. Hind wing slightly longer and narrower than in C. simile (now a synonym of Procloeon simile).

Abdominal tergites 2-6 pale whitish, hyaline; a geminate ruddy dorsal line is present; posterior margins shaded broadly with ruddy, and with lateral wedge-shaped markings extending forward from these, halfway to the anterior margin. From near the apex of each wedge an oblique ruddy streak extends inward to the anterior margin; these streaks are most clearly marked on tergites 5 and 6, tending to break up into spots on tergites 2 to 4. Tergites 7-10 deep maroon brown. Sternites pale yellowish white; hyaline on 2-6, the apical sternites opaque with slight ruddy shading. Forceps and tails white.

The bright red eyes of dried specimens separate this species from the allied C. simile, in which the eyes are blackish brown; the thorax is also paler than in that species. From C. bellum (now a synonym of Procloeon bellum) it may be distinguished by the broader banding on the abdomen and the narrower hind wings.