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 5 records from GBIF, adults of this species have been collected during April (80%) and October (20%).
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.
This is a rather large blackish species with brown wings. Head and thorax above shining black; sides of the latter paler in the sutures. Fore legs nearly uniform dark brown; middle and hind legs pale brown. Wings brown at the roots, and with a brown cloud covering more than the apical half of the fore wings and about half of the hind wings. The inner margin of the brown in the fore wings is angulated at the outer fork, behind which it is abruptly widened. The cross veins in the clear area before it are pale brown, even in the costal strip. In the stigmatic area they are numerous, irregular, and in the middle portion, anastomosing at midway their height. Costal and subcostal cross veins in the hind wing are about equal in number. All longitudinal veins are brown.
Abdomen brown, darker on both ends, hardly paler beneath but distinctly paler on the joinings of the middle segments, giving this part a ringed appearance. Tails nearly uniform brown. Middle tail one-fourth as long as the others.
Genitalia yellowish brown, of the usual form with small apical tooth of the penes directed laterally, and the long arcuate reflexed spur as long as the cleft between the penes is deep.
Described as B. vibex
Body length 13 mm, wing length 10-12 mm
This is a dark brown species with an oblique streak of brown across the fore wing. Face yellowish with brown sutures. Antennae brown. Top of head blackish. Thorax dark brown with pale streaks in the lateral sutures. Fore legs brown, the femora a little reddish. Middle and hind legs yellowish brown. Wings hyaline with brown veins and with an oblique streak that overspreads the stigmatic area and, narrowing to rearward, extends across the base of the bisector of the outer fork almost to the hind margin. Costal cross veins faint except in the stigmatic area, where they are crowded and irregular, a few of them forking or anastomosing. Hind wing hyaline.
Abdomen brown, darker on the ends, with obscure pale lines on the lateral margins and on the joinings of the middle segments. Tails brownish, narrowly and regularly ringed with black; middle tail a third as long as the others. Genitalia yellowish brown. Apical tooth of penes acuminately pointed and inclined obliquely to rearward. Reflexed spur rather slender, its tip barely reaching to the level of the bottom of the cleft between the penes. The latter is deeper than the cleft between the obliquely triangular lobes of the 9th sternite (see fig. 138.)
The male subimago has shorter tails (17 mm.) with the middle one less reduced (8 mm.), and with little indication of the basal hyaline area of the wings, these being brown, and only a little paler toward the anal angle. The brown of the body is paler, with the scutellum mostly yellowish and with yellow lines on most of the sutures of the mesothoracic dorsum. On each abdominal segment is a pair of basal oblique dashes, plainest toward basal segments, with a faint pale median longitudinal line between them. The female imago is similar to the male.