Mayfly Species Tricorythodes stygiatus (Tricos)

Mesonotum shiny blackish; thoracic sternum and abdomen dull blackish; hind femora deep rufo-piceous, tibiae largely same color.

Head dull black, the posterior tubercles shiny black; eyes and lateral ocelli black; basal joint of antenna black, paler apically. Median area of pronotum dull black, with faint ruddy tinge in the mid-dorsal portion; shiny black laterally. Mesonotum shiny black, the scutellum with ruddy tinges; pleura shiny black; anterior to the wing roots and around the bases of the legs are dull areas. Sternum dull black. Coxa and trochanter of fore leg black; femur blackish with a pale hyaline streak longitudinally; tibia and tarsus whitish, tinged faintly with ruddy; tibia 1.5 mm. in length. Coxae and trochanters of middle and hind legs blackish, femora shiny rufo-piceous; tibiae largely rufo-piceous, becoming paler apically; tarsi whitish. Wings whitish hyaline; subcosta and radius darker. Abdominal tergites completely suffused with dull blackish, tinged slightly with ruddy in the median area, especially on the basal tergites. Sternites dull blackish; lateral margins somewhat shiny; posterior margins faintly whitish. Genitalia dull whitish (see fig. 160). Tails blackish basally, becoming pale smoky apically.

The black body and deep reddish brown femora separate this from other small species in the genus.