Mayfly Species Anafroptilum bifurcatum (Tiny Sulphur Duns)

Abdominal tergites 2-6 of male imago yellowish white, with traces of ruddy shading on the posterior margins of 2-4, and a faint reddish dorsal line. Hind wing relatively wide.

Head blackish, also the basal half of the antennae. Thorax deep olive brown. A pale yellow line extends forward from the wing base along the lateral margin of the mesonotum, ending in a small round yellowish patch. Posterior margin of mesonotum and pleural sutures yellowish. Legs pale yellowish white, femora somewhat deeper in color. Wings hyaline. Hind wing relatively wider than in most species of this genus; in some specimens, but not all, the lower of the two longitudinal veins may be faintly forked near its apex (see fig. 165).

Abdominal segments 2-6 hyaline, yellowish white; a faint reddish dorsal hair-line, and traces of ruddy shading on the posterior margins of tergites 2-4, extending to the spiracular line. Tergites 7-9 deep chocolate brown; 10 pale yellowish. Sternites 7-9 alabaster white. On the pale tergites, a broken blackish line marks the spiracular area. Forceps and tails whitish. Plate between forceps bases large, somewhat dome-shaped; a small pointed tubercle is borne on it (see fig. 166).

The greater width of the hind wing separates this species from C. rufostrigatum (now a synonym of Procloeon rufostrigatum), which it resembles superficially. Of three specimens in the Cornell collection, in one of these only, the forking of the second vein in the hind wing appears. In each, however, there are faint traces of cross veins in the hind wing, 3 to 5 in each of the three spaces; in two of these, an interrupted third longitudinal vein occurs, its basal and apical portions missing. The second joint of the forceps is slightly irregular on the inner margin, but lacks a definite tubercle or projection as in C. conturbatum (now a synonym of Anafroptilum conturbatum). In these specimens, the scutellum is prominently pale yellowish white. The presence of the small pointed tubercle between the forceps bases allied this species with C. semirufum (now a synonym of Anafroptilum semirufum), from which it may be distinguished by the much wider hind wing and the duller brown of the posterior tergites.