Mayfly Species Neocloeon triangulifer

Thorax: Legs pale, a dark longitudinal stroke about the middle of the forefemur and an indistinct dark band subapically in other femora.

Abdomen: An indistinct and discontinuous median dorsal dark line; situated submedially on the anterior border of each segment or very near it a distinct rounded dark spot surrounded by a pale area; lateral borders of segments pale with a dark quadrate mark before the middle; an indefinite dark area between the pale lateral border and the mid-line; venter pale with a lateral dark area in each segment and a pair of submedian dark spots on anterior border of segments 7, 8 and g; caudal filaments stout; the laterals spinulose on lateral border; gills simple lamellae on all segments with conspicuous tracheae, the branches on most gills all directed medially from the main tracheal trunk, in the fourth gills weak lateral branches also as shown in figure.

Only the female imago of this species is known; distinct because of the triangular light brown lateral patches on sternites 2-7.

Head almost wholly light pinkish brown, slightly paler near the eyes. Thorax rather deep brown; sternum only slightly paler than notum; pleura tinged slightly with ruddy. Legs pale dull yellowish. Wings hyaline; venation faintly amber-tinged; cross veins almost invisible except in the stigmatic area. Abdominal tergites brown, faintly tinged with ruddy, especially on the posterior ones; sternites pale yellowish; on sternites 2-7 are triangular light brown lateral patches, based on the anterior margin and reaching almost to the posterior border; these patches are barely visible on sternites 8 and 9. Tails pale.

The darker thorax, especially the sternum, and the lateral brown triangles on the sternites, serve to separate the females of this species from those of C. rubropictum (now a synonym of Procloeon rubropictum).