Mayfly Species Siphlonurus autumnalis (Gray Drakes)

A large dark species occurring in the late summer.

Head blackish. Pronotum deep smoky. Mesonotum dark brown, the scutellum blackish brown. Pleural sutures pale yellowish. Sternum blackish brown.

Fore leg deep blackish. Middle and hind legs dull yellowish with a smoky tinge; tarsi distinctly smoky. Wings hyaline; longitudinal and cross veins deep brown. Cross veins weak in the basal two-thirds of the costal space; in the stigmatic area heavier and strongly anastomosed.

Abdomen deep purplish brown dorsally, the pale anterior triangles tinged with yellow. Lateral margin narrowly yellowish, especially on the four apical segments. Ventrally deep purplish brown, the posterior margins narrowly yellowish. The median portion of the posterior half of sternite 9 shaded indistinctly with yellow, which extends over to the anterior margin of the forceps base. Remainder of forceps base, and forceps, deep smoky. The first joint of the forceps is rounded on its inner margin. The apical margin of the forceps base, between the forceps, is weakly excavated, and is on a level with the apex of the first joint of the forceps.