Mayfly Species Procloeon caliginosum (Tiny Sulphur Duns)

Abdominal tergites 2-6 of male imago pale translucent with very faint tinge of brown.

Turbinate eyes deep blackish brown in dried specimen. Head and thorax deep brown. Lateral margin of mesonotum, the sutures, and a small patch anterior to the scutellum, paler brown. Legs dull whitish; fore legs tinged with smoky. Wings hyaline, venation pale; 6 to 7 cross veins in the stigmatic area of the fore wing; intercalary of first interspace missing. Hind wing long and narrow, the costal projection strong. Abdominal segments 2-6 pale translucent, the tergites very faintly tinged with brown, particularly along the lateral and posterior margins. Tergites 7-10 chocolate brown, sternites paler. Forceps and tails whitish. A well developed inward bulge is present on the inner margin of the second forceps joint.

This species, related to C. rufostrigatum (now a synonym of Procloeon rufostrigatum), lacks entirely the reddish abdominal markings of that species, is also considerably larger, and has a much better developed bulge on the second forceps joint. It is distinguished from the allied C. bellum (now a synonym of Procloeon bellum) by the absence of ruddy markings on the tergites.