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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.

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Mayfly Genus Cinygmula (Dark Red Quill)

This is primarily a Western genus. Cinygmula ramaleyi is the most important species, producing good hatches in the West. Cinygmula reticulata may also be relevant, and I have seen a great spinner swarm from an unsung species, Cinygmula par, in the Washington Cascades.

There is only one Eastern species, Cinygmula subaequalis, and its importance is minor.

Where & when

I have found different Cinygmula species emerging throughout the summer and fall in Washington and Alaska.

In 74 records from GBIF, adults of this genus have mostly been collected during May (34%), June (24%), April (15%), July (14%), and August (7%).

In 57 records from GBIF, this genus has been collected at elevations ranging from 240 to 10971 ft, with an average (median) of 4524 ft.

Genus Range

Hatching behavior

Most Cinygmula duns emerge in the surface film, but in some cases they may escape their nymphal shucks while still drifting to the surface.

Egg-Laying behavior

The angling literature suggests that Cinygmula spinner falls are too sporadic to be important, but I have seen Cinygmula par swarming in very good numbers, albeit on a small stream where hatch-matching wasn't needed because the hungry trout would hit anything anyway.

Nymph biology

Cinygmula nymphs can withstand slower water than many of the other genera in the Heptageniidae family.

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

Body length: 8 mm
Wing length: 9-10 mm

A medium-sized species, wings tinged with light grey, darker at bases; dark midventral ganglionic marks.

Thoracic notum light pitch-brown, “sometimes approaching light luteo-piceous anteriorly at the sides” (Eaton). Legs sooty to golden brown; base of fore femur and trochanter somewhat paler, base of first fore tarsal joint darker. Wings hyaline, “tinted with light bistre-grey throughout, but with a stronger tint than elsewhere” at the wing roots and in the stigmatic area; near wing roots the color becomes rather dark brown. Venation yellowish brown.

Abdominal segments 2-7 semi-hyaline; tergites largely light brown, the anterior ‘margins, antero-lateral areas, narrow median line and submedian streaks being hyaline, “dirty-whitish.” The three pale longitudinal streaks are outlined in darker color. Sternites paler, the ganglionic areas on 3-7 conspicuously marked with sepia-brown. Segments 8-10 opaque; tergites “Vandyke-brown,” sternites “very light brownish ochre” (Eaton). Tails brown. A large spine on lower outer margin of penes on each side, smaller spine on inner margin (see fig. 103).

This species is allied to both C. confusa and hyalina, also to the eastern C. atlantica. Distinguishing features are indicated under each of these species.

Specimens of the Mayfly Genus Cinygmula

3 Male Duns
7 Female Duns
12 Male Spinners
6 Female Spinners
13 Nymphs

4 Streamside Pictures of Cinygmula Mayflies:

Discussions of Cinygmula

Red Heptagenia?
30 replies
Posted by GONZO on Jul 19, 2011
Last reply on Jul 24, 2011 by PaulRoberts
The gills and protruding mouthparts make me think that this might be Cinygmula. I've seen red phase Rhithrogena nymphs, but have never seen this coloration in Cinygmula (or Heptagenia).

Start a Discussion of Cinygmula


  • Arbona, Fred Jr. 1989. Mayflies, the Angler, and the Trout. Nick Lyons Books.
  • Caucci, Al and Nastasi, Bob. 2004. Hatches II. The Lyons Press.
  • Knopp, Malcolm and Robert Cormier. 1997. Mayflies: An Angler's Study of Trout Water Ephemeroptera . The Lyons Press.
  • Mayo, V.K. 1952. New Western Ephemeroptera, IV, With Notes. The Pan-Pacific Entomologist 28(4): 179-186.
  • Needham, James G., Jay R. Traver, and Yin-Chi Hsu. 1935. The Biology of Mayflies. Comstock Publishing Company, Inc.
  • Slater, J. and Kondratieff, B.C. 2004. Review of the Mayfly Genus Cinygmula McDunnough (Ephemeroptera: Heptageniidae) in Colorado. Journal of the Kansas Entomological Society 77(2): 121-126.

Mayfly Genus Cinygmula (Dark Red Quill)

Genus Range
Common Name
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