Mayfly Species Rhithrogena flavianula

A large species of the brunnea group, having basal lateral spines on penes.

Clypeus dull grey, “crossed by a black band at its base” (McD.). Head ochreous at bases of antennae and around ocelli. Thorax deep brown. Anterior to the wing roots a pale ochreous patch, within which are two blackish streaks. Pleural sutures and bases of wings with ochreous markings. Fore leg blackish. Middle and hind legs golden brown; a black streak on basal half of each femur; tarsi blackish. Wings hyaline; stigmatic area tinged with pale amber. Venation blackish-brown. Abdominal segments deep reddish brown; lateral and posterior margins of tergites narrowly light yellow, so that abdomen appears annulate. Posterior sternites darker in color, the posterior margins yellow-banded as on the dorsum. Forceps deep brown. Tails blackish. Penes distinctly outcurved at tip, each bearing a series of very small spines near apex and on lateral margin. A large spine laterally at base on outer margin (see fig. 100).

The annulate abdomen, large size and genitalic structures should serve to distinguish this from other allied species.