Mayfly Species Siphlonurus phyllis (Gray Drakes)

A rather large species having a conspicuous dark ventral stripe.

Head and thorax blackish brown. Thorax with yellowish shadings on the anterior portions. Legs dull olive brown; femora with apical brown bands. Wings hyaline, faintly tinged with brown in the basal area. Veins dark.

Abdomen dark brown dorsally. Dark oval spots and lateral triangles present. The pale anterior triangles are yellow, this color extending along the lateral margin. Ventrally yellowish. A brown mid-ventral stripe is present, and two small brown dots in each sternite, touching the median stripe. Anterior to the small dots, and laterad of them, are two large brown dots. Light brown shading along the lateral margin, in place of the usual lateral patches. Sternite 9 largely pale yellow, diffusely shaded with brown in the median area; a deep brown lateral streak on each side. Postero-lateral edge of sternite 9 produced into a prominent sharp tooth or spine. Forceps base squarely truncate on its apical margin. Forceps pale yellowish. Tails whitish. Genitalia as in fig. 123.

The nymph of this species has double gills, on each gill-bearing segment of the abdomen. The legs are banded, and the tail has the usual black band beyond the middle.