Header image
Enter a name
Lateral view of a Female Hexagenia limbata (Ephemeridae) (Hex) Mayfly Dun from the Namekagon River in Wisconsin
Hex Mayflies
Hexagenia limbata

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.

Case view of a Pycnopsyche guttifera (Limnephilidae) (Great Autumn Brown Sedge) Caddisfly Larva from the Yakima River in Washington
It's only barely visible in one of my pictures, but I confirmed under the microscope that this one has a prosternal horn and the antennae are mid-way between the eyes and front of the head capsule.

I'm calling this one Pycnopsyche, but it's a bit perplexing. It seems to key definitively to at least Couplet 8 of the Key to Genera of Limnephilidae Larvae. That narrows it down to three genera, and the case seems wrong for the other two. The case looks right for Pycnopsyche, and it fits one of the key characteristics: "Abdominal sternum II without chloride epithelium and abdominal segment IX with only single seta on each side of dorsal sclerite." However, the characteristic "metanotal sa1 sclerites not fused, although often contiguous" does not seem to fit well. Those sclerites sure look fused to me, although I can make out a thin groove in the touching halves in the anterior half under the microscope. Perhaps this is a regional variation.

The only species of Pycnopsyche documented in Washington state is Pycnopsyche guttifera, and the colors and markings around the head of this specimen seem to match very well a specimen of that species from Massachusetts on Bugguide. So I am placing it in that species for now.

Whatever species this is, I photographed another specimen of seemingly the same species from the same spot a couple months later.
27" brown trout, my largest ever. It was the sub-dominant fish in its pool. After this, I hooked the bigger one, but I couldn't land it.
Troutnut is a project started in 2003 by salmonid ecologist Jason "Troutnut" Neuswanger to help anglers and fly tyers unabashedly embrace the entomological side of the sport. Learn more about Troutnut or support the project for an enhanced experience here.

Mayfly Species Leucrocuta umbratica

Where & when

In 4 records from GBIF, adults of this species have been collected during June (75%) and August (25%).

Species Range

Physical description

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.

Male Spinner

Described in Needham et al (1935) as Heptagenia umbratica
Body length: 7-8 mm
Wing length: 8-9 mm

Mesonotum brown; abdominal tergites 2-6 pale yellow, posterior margins black, with brown lateral patches; genitalia as in fig. 95.

Frontal portion of head light yellow; frontal shelf semi-hyaline with a blackish streak; vertex brown. Thoracic notum and pleura brown; sternum light yellow. Legs pale yellowish, with scattered black streaks at their bases; fore femur slightly deeper yellow, fore tibia and tarsus smoky; basal joint of fore tarsus about 1/5 of the second, which is slightly shorter than the third. Wings hyaline; longitudinal and cross veins in costal half of fore wing brownish, all other veins pale; 3 to 4 basal costal cross veins.

Abdominal segments 2-6 light yellow, semi-hyaline; tergites narrowly black on the posterior margins, and with brown triangular submedian lateral patches based on the posterior margin, the apex rather blunt and not quite reaching the anterior margin. Segments 7-10 opaque; tergites brown, with the dark lateral patches faintly indicated; sternites shaded with brown. Forceps creamy, tinged with brown basally. Tails whitish, unmarked. Penes distinctly reminiscent of the maculipennis (now a synonym for Leucrocuta maculipennis) group, although the lack of shading on the cross veins separates it from species of that group.

Start a Discussion of Leucrocuta umbratica


  • Needham, James G., Jay R. Traver, and Yin-Chi Hsu. 1935. The Biology of Mayflies. Comstock Publishing Company, Inc.

Mayfly Species Leucrocuta umbratica

Species Range
Troutnut.com is copyright © 2004-2023 (email Jason). privacy policy