Mayfly Species Siphlonurus mirus (Gray Drakes)

A large species, rather pale in color, with a conspicuous dark area on the hind wing.

Head yellowish brown. Thorax dark brown. Metanotum, except the areas on each side of the scutellum, yellowish to olive brown. Scutella yellowish. Pleural sutures cream colored. Pale bands anterior to wing roots; anterior to bases of middle and hind leg; and across the mesosterna and metasterna. Fore leg amber, the joinings and the two distal segments of the tarsus brown. Middle and hind legs yellowish; tarsi and all joinings brown, a diffuse smoky band on the femur. Fore wing hyaline, the longitudinal veins purplish black, those of the costal margin heavier. Cross veins light purplish black except in the costal space; these are pale and almost invisible. Stigmatic cross veins simple, almost straight, neither forking nor anastomosing. Hind wing dark brownish black, hyaline only at the base and in the basal half of the costal space. Cross veins in dark area margined with smoky brown. The extent of the hyaline space at the base of the wing varies with the sex, being more restricted in the male.

Abdomen yellowish brown, middle segments semi-hyaline. Posterior margins of tergites dark brown, widest at the middle line. The entire lateral margin also dark brown, except a pale line in the posterior angle. Dark lateral triangles reduced to small areas in the postero-lateral angle, and along the lateral margin; dark oval spots more or less apparent. Tergites 9 and 10 reddish brown. Ventrally yellowish brown on middle segments. Sternites 1 and 2, and the apical part of 3, dark reddish brown. Apical sternites may be largely yellow, with a dark brownish median line. Posterior half of each middle sternite shaded with brown, the extreme posterior margin whitish. A dark triangle runs forward from the posterior dark band, on each side of the median line, enclosing a small round spot. A dark oblique oval spot is often present, anterior to the center of each sternite, on each side. Mid-ventral line white in anterior half of each basal and middle sternite. Tails yellowish white, joinings reddish brown. Penes as in fig. 121.

The nymph has a conspicuous oblique black band on the front of the head, extending from below the antenna to the lower margin of the eye. Legs without dark bands; no dark transverse band across the tails. Gills double on segments 1 and 2 only. Ventral markings rather similar to those of the imago.