Mayfly Species Hexagenia rigida (Great Olive-Winged Drakes)

Abdominal tergites largely brown with yellow submedian and lateral blotches; usually a wavy brown lateral stripe on each side of venter, no dark triangles on middle sternites; penes long, almost straight.

Head yellow; vertex suffused with reddish brown. Eye olive brown above; eyes separated by space about equal to one eye diameter. Pronotum pale yellow, lateral stripes wide, purplish black. Mesonota and metanota light reddish brown, the posterior portions yellowish; tips of scutella blackish; pleura light red-brown. Sternum reddish to purplish brown, deepest on posterior of prosternum. Ventral portion of fore coxa deep purplish black; trochanter, femur and tibia reddish brown; tarsus may be reddish brown except base of second joint, or each middle joint may be yellowish basally. Middle and hind legs pale yellow; tarsal joinings and last tarsal joint purplish brown. Wings hyaline; costal margin of fore wing light olive brown; all veins blackish brown. Cross veins of costal margin heavily black; a few nearer the disc may be narrowly margined; in hind wing, several in disc usually margined, forming several small blackish spots. Outer margin of hind wing typically with narrow dark margin, but this may be lacking.

Abdominal tergites mainly brownish; yellowish triangular submedian blotches and smaller blotches next to lateral margin, on each tergite; the yellow areas may be quite bright in color, or more or less obscured by a reddish tinge. Posterior margins usually narrowly pale. Sternites pale yellow; a purplish black blotch in each anterolateral angle, an oblique lateral stripe attached to its posterior end, so that lateral stripes appear to extend “from the central area of one segment, backwards to the middle of the lateral margin of the following segment” (McDunnough). Ends of these stripes usually connected, so that a more or less continuous wavy lateral line is formed. Mid-ventral line deep brown on apical segments; often traces of dark line here on other segments; apical sternites with median dark triangles which do not attain the anterior margin. Forceps brown, second joint yellow. Penes rather long, almost straight (see fig. 84). Tails pale yellow, each joining narrowly purplish brown.

The long straight penes are distinctive.