Mayfly Species Siphlonurus decorus (Gray Drakes)

A medium-sized species with conspicuous ventral markings.

Head brownish. Thorax dark olive brown. A large pale patch near the center of the pleura on each side. Pleural sutures pale; purplish rose markings on pleura and notum. A narrow pale transverse band crosses each division of the sternum.

Legs light brown, joinings darker. Femora with apical dark bands. Purplish rose spot on each coxa. Wings hyaline; longitudinal veins of fore wing purplish brown; all other veins pale brown. Costal cross veins before the bulla very pale, almost invisible. In the stigmatic area, pale but distinct; numerous, slightly curved, tending to anastomose. Stigmatic area, also the corresponding subcostal space, opaque white.

Abdomen dark olive brown dorsally, pale ventrally. Usual dark lateral triangles present on tergites; oval spots distinct. Mid-dorsal line pale; pale anterior triangles quite extensive. Ventrally, a blackish mid-ventral line extends continuously from the posterior margin of sternite 1 to the posterior margin of sternite 9, widened at each margin of each sternite. At center of each sternite, a small black dot on each side is very close to the dark median line. Anterior to this small spot, and laterad of it, is a larger dark brown oblong spot. The usual lateral patches are represented only by a narrow dark brown line parallel to the pleural fold. Sternites 7 and 8, and the posterolateral angles of sternite 9, powder white.

Forceps and forceps base light brown with purplish rose markings. Penes shown in fig. 123. Tails dark brown basally, becoming light tan in the distal portion. Joinings dark purplish brown.