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Pale Brown Duns

Like most common names, "Pale Brown Dun" can refer to more than one taxon. They're previewed below, along with 6 specimens. For more detail click through to the scientific names.

Mayfly Species Rhithrogena hageni

These are very rarely called Pale Brown Duns.
According to Fred Arbona in Mayflies, the Angler, and the Trout, this is an excellent hatch and one of the most common fast-water mayflies in the West.
Rhithrogena hageni (Western Black Quill) Mayfly NymphRhithrogena hageni (Western Black Quill) Mayfly Nymph View 9 PicturesI'm basing the ID of this near-mature nymph on a male spinner with similar size and markings, collected on the same trip. There isn't a key to reliably identify the nymphs of most Rhithrogena species otherwise.
Collected July 4, 2020 from in
Added to Troutnut.com by on July 12, 2020
Female Rhithrogena hageni (Western Black Quill) Mayfly DunFemale Rhithrogena hageni (Western Black Quill) Mayfly Dun View 7 PicturesI was surprised by the olive cast on the body of this female Rhithrogena dun, which led me to mistake it for a western green drake (Drunella) in the field. I was pleasantly surprised to get a closer look and find something I hadn't collected yet. Its species ID is based on proximity to male spinner collected on the same trip, as well as physical similarity (size, tergite (
One tergite of this Isonychia bicolor mayfly spinner is highlighted in red.
One tergite of this Isonychia bicolor mayfly spinner is highlighted in red.
Tergite: The top (dorsal) part of a single segment on an insect's abdomen when it consists of a single chitinous plate (sclerite), or an individual sclerite if the segment has more than one.
)
coloration, dark streaks on the femora (
The femur of this Isonychia bicolor mayfly spinner is highlighted in red.
The femur of this Isonychia bicolor mayfly spinner is highlighted in red.
Femur: The main segment of an insect's leg close to the body, in between the tibia and the trochanter.
)
) to that specimen.
Collected July 4, 2020 from in
Added to Troutnut.com by on July 12, 2020
Male Rhithrogena hageni (Western Black Quill) Mayfly SpinnerMale Rhithrogena hageni (Western Black Quill) Mayfly Spinner View 14 PicturesAlthough I could not find the preserved specimen to examine under my good new microscope, I'm tentatively calling it one Rhithrogena hageni, based on apparent similarity to this specimen, which I was able to positively ID.

The relative angle of the penes (Penes: The paired genital structures of most male insects, which vary widely in form and are one of the main characteristics used for species identification.) is a bit shallower in this specimen, but I photographed another specimen from the same collecting trip (and I think even the same swarm, although I don't recall for sure) as the other one, and it had the shallower angle seen on this specimen. I'm guessing it's just variation within the species.
Collected July 8, 2019 from in
Added to Troutnut.com by on July 18, 2019

Mayfly Species Cinygmula reticulata

These are very rarely called Pale Brown Duns.
Cinygmula reticulata is probably the second most important species of Cinygmula behind Cinygmula ramaleyi, perhaps because the waters where it can be found in good numbers are often more remote. They have been reported as abundant in many high country streams of the Southern Rockies as well as the High Sierra's Eastern slope. An obvious difference in their coloration may be the easiest way to tell them apart. Cinygmula ramaleyi is more somber with a brownish body and dark gray wings and is often confused with the similar sized and colored Ephemerella tibialis, in spite of the difference in tail counts. Cinygmula reticulata on the other hand is a bright cinnamon dorsally with pale creamy legs and pale wings that are often a brilliant canary yellow. This is one of North America's most beautiful mayflies.
Cinygmula reticulata (Western Ginger Quill) Mayfly NymphCinygmula reticulata (Western Ginger Quill) Mayfly Nymph View 1 PicturesI collected several live specimens of nymphs and reared them to the imago (Imago: The sexually mature adult stage of the mayfly is called the imago by scientists and the spinner by anglers.) stage. They were C. reticulata. The interesting thing is they were collected in May and were emerging along with Rhithrogena (March Brown). This seems to be an overlooked hatch since in some rivers it emerges very early, before runoff.
Collected May 10, 2009 from in
Added to Troutnut.com by on June 26, 2011
Female Cinygmula reticulata (Western Ginger Quill) Mayfly DunFemale Cinygmula reticulata (Western Ginger Quill) Mayfly Dun View 1 Pictures
Collected June 15, 2011 from in
Added to Troutnut.com by on June 24, 2011
Male Cinygmula reticulata (Western Ginger Quill) Mayfly SpinnerMale Cinygmula reticulata (Western Ginger Quill) Mayfly Spinner View 7 PicturesThe lengths of the wing and body, measured with a caliper, are both 8 mm.

Keys in Needham's 1935 Biology of Mayflies point to either Cinygmula reticulata or Cinygmula gartrelli. IT seems to have “cross veins in costal half of fore wing only, slightly margined with brown” and “wings tinged withamber at base and along costal margin of both wings” (gartrelli) as opposed to “all cross veins of both wings faintly but broadly margined with pale smoky” and “wings entirely amber-tinged” (although there is a slight amber tinge throughout, just more pronounced in places) as in reticulata. However, wing length reported for reticulata (9 mm) is closer to this specimen than gartrelli (10 mm). Ventral (Ventral: Toward or on the bottom.) median marks are supposed to be “traces” for reticulata and “present” for gartrelli. Descriptions for both species involve semi-hyaline (Hyaline: Highly transparent, or glassy; usually refers to insect wings, especially those of mayfly spinners.) anterior (Anterior: Toward the front of an organism's body. The phrase "anterior to" means "in front of.") abdominal segments not present on my specimens. Distribution records suggest reticulate lives nearby, so I'm going with that, but I can't confidently rule out gartrelli.
Collected August 1, 2020 from in
Added to Troutnut.com by on August 18, 2020
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