The famous nocturnal Hex hatch of the Midwest (and a few other lucky locations) stirs to the surface mythically large brown trout that only touch streamers for the rest of the year.
In 15 records from GBIF, adults of this species have been collected during August (40%), June (20%), April (20%), September (7%), July (7%), and May (7%).
In 9 records from GBIF, this species has been collected at elevations ranging from 4951 to 6854 ft, with an average (median) of 5230 ft.
Most physical descriptions on Troutnut are direct or slightly edited quotes from the original scientific sources describing or updating the species, although there may be errors in copying them to this website. Such descriptions aren't always definitive, because species often turn out to be more variable than the original describers observed. In some cases, only a single specimen was described! However, they are useful starting points.
Mesonotum with dark brown median stripe; costal margin of fore wing tinged with pale lemon yellow; cross veins brown; dark dorsal stripe on abdomen; genitalia of the Heptagenia pulla type; probably allied to that species.
Head light brown; black dash on frons next to eye, below base of antenna; vertex with ruddy tinge. Thoracic notum brown, with a deeper brown mid-dorsal stripe, most evident on anterior portion of mesonotum. Pleura pale ochreous brown; short black streaks just beyond bases of middle and hind coxae, and similar streaks above these, in line with wing roots; all of these dark markings may be obscure. Legs pale yellowish brown; all the femora, the fore tibia, and joints of the fore tarsus tipped with purplish. Basal joint of fore tarsus about 1/4 of the second; basal joint of hind tarsus slightly shorter than second. Wings hyaline; costal margin tinged with pale lemon yellow. Basal half of subcosta and radius thickened, pale yellowish; other longitudinal veins fine, deep brown. Cross veins thicker than longitudinals, especially along the costa; deep brown.
Abdominal segments very pale brownish. Tergites 2-7 with a dark purplish-brown median stripe enclosing a narrow pale mid-dorsal line; on posterior margins a narrow dark band of same color, with submedian broad dark bands projecting forward from it, but not attaining the anterior margin. The dark dorsal and submedian stripes may coalesce to form a simple dark shading, or with paler lunate marks submedially from the anterior margin. Tergites 8-10 opaque, light reddish brown; sternites paler. Forceps ochreous; tails dull ochreous, joinings narrowly brown. Genitalia of the pulla type; upper pair of median spines smaller than lower ones.
Larger and paler than H. criddlei (now a synonym of Ecdyonurus criddlei) another dark species of this group; apparently close to H. pulla, but rather darker in color markings, and with darker legs and tails.