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.
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.
Head blackish brown; frontal margin pale. Eyes dull orange. Thorax very dark olive brown. Mesonotal scutellum and its lateral margins, the lateral margins of the mesonotum, and most of the sternum, blackish brown. Ganglionic areas blackish. Pleura dark brown with yellowish interspaces. Fore femur yellowish at base, the apex brown; tibia deep olive brown; tarsus paler smoky brown. Middle and hind legs yellowish white, with dark pencilings on the femora at base and apex; tibiae brownish at base; tarsi pale smoky brown. Wings hyaline; longitudinal veins dark purplish brown, cross veins of the fore wing finer but distinctly dark. A dark reddish brown spot at the base of the subcosta and radius of fore and hind wings, and a dark streak at the base of the anal region of the fore wing. Stigmatic area opaque whitish; cross veins anastomosed.
Abdomen smoky to olive brown dorsally; tergites 1-2 and 7-8 shaded with blackish brown, middle tergites reddish brown in the median area. A dark brown line above the pale pleural fold, containing a dark stigmatic spot and a dark crescent, and two or three pale areas. Base of tergite 9, and most of 10, yellowish. Posterior margins narrowly pale. Ventrally pale yellowish white with wide brownish black anterior margins and lateral triangles on each sternite; ganglionic areas blackish; sternites 8 and 9 largely brownish black. Tails black at base, deep brown distally; joinings indistinctly darker. Genitalia dark smoky brown. Third joint of forceps short, stout, conical. Penes separated at apex by a wide V-shaped cleft; no spines are present (see fig. 156).
Described as E. euterpe
Body length 10-11 mm, wing length 10-11 mm
A member of the Ephemerella needhami group; venation light reddish brown; genitalia without spines; prominent dark ventral markings in nymph and imago; nymph without dorsal spines.
Head dark brown, frontal margin paler; eyes light orange. Thorax reddish brown. Pronotum shaded with smoky brown; mesonotum margined with darker brown, and with narrow median and submedian streaks on the scutum; scutellum outlined with black, its lateral margins dark red-brown. Two dark streaks on the pleura. Sternum light reddish brown with darker brown areas; ganglionic areas blackish. Legs yellowish. Fore femur tinged with smoky at base and apex; a small dark reddish brown spot at the apex. Distal joint of fore tarsus, and claws and tarsal joinings of all tarsi, pale smoky. Very small spines on the fore tibia. Wings hyaline; stigmatic area opaque whitish, the cross veins anastomosed near the costal margin. Longitudinal veins light reddish brown, those of the anal area wholly pale, as are all the cross veins.
Abdomen dorsally light reddish brown tinged with olive, the apical segments darker. Anterior margins narrowly dark, posterior margins pale; pleural fold pale, paralleled above by a dark line containing a dark stigmatic dot and a small pale oblong area. Traces of a pale median line and of pale submedian streaks on the basal tergites. Venter pale yellowish white; anterior margin of each apical sternite, and broad lateral triangles on all the sternites, deep purplish brown. Sternites 7-9 largely dark; ganglionic areas blackish brown. Tails dark purplish brown basally, somewhat paler distally; joinings not distinct. Genitalia reddish brown; terminal joint of forceps short, thick, conical. Penes separated apically by a V-shaped cleft; no spines are present (see fig. 155).
Nymph yellowish to pale yellowish brown with brown markings. Head smooth (see fig. 151 a). Genae produced anteriorly and laterally to form a frontal shelf overhanging the mouthparts. Thorax smooth; dark brown spots and pencilings on each side of the pronotum, and anterior to the wing roots on the mesonotum. Legs yellowish white; tibiae marked narrowly at each end with dark reddish brown; apex of tarsus and tip of claw dark red. Femora moderately flattened; long hairs on the posterior margins of femora and tibiae. 3 to 4 short blunt denticles on each claw. Well developed lateral extensions on the abdominal segments, each bearing a posterolateral spine. No dorsal spines. Gills present on segments 3-7. Tergites 1-2, 5-6 and the median and lateral areas of 7, shaded with reddish brown; dark lateral patches on these tergites. Ventrally yellowish, with brownish black anterior margins and lateral triangles on all sternites, as in the imago. Ganglionic areas darkened. Tails pale yellowish white, tips dark brown; two dark reddish brown bands at the base.
Described as E. euterpe
Nymph light reddish brown; a few indistinct darker markings on the thorax; legs fringed with hairs; tips of femora and tibiae, both ends of the tarsi, and claws, dark reddish brown; 4 to 5 pectinations on each claw. Apical tergites distinctly reddish. Broad lateral triangles mark each sternite, as in the imago. Tails blackish brown at the base, reddish brown distally. Two or three narrow dark bands near the base. Beyond the basal third, tails fringed with rather long hairs. Head and thorax smooth. Genae produced laterally and anteriorly to form frontal shelf. Gills on segments 3-7. Lateral extensions of the abdomen quite prominent; each bears a postero-lateral spine. No dorsal spines.