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.

The Clark's Fork of the Yellowstone River in Wyoming

Stream photos

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Isoperla (Stripetails and Yellow Stones) Stonefly Adult Isoperla (Stripetails and Yellow Stones) Stonefly Adult

Dorsal view of a Isoperla (Perlodidae) (Stripetails and Yellow Stones) Stonefly Adult from Mystery Creek #308 in Washington

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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.

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Mayfly Species Procloeon quaesitum (Tiny Sulphur Duns)

Species Range

source

Map of specific collection sites

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 Centroptilum quaesitum

Body length: 7 mm
Wing length: 7 mm

Abdominal tergites 2-6 of male imago bright ruddy, except for a narrow pale lateral area.

Turbinate eyes light orange-red in dried specimen. Head light yellowish, as are the basal joints of the antennae; antennal filament smoky. Thorax rather light brown, the pleura with faint ruddy tinges; a yellow streak anterior to the wing root. Sternum yellowish, with ruddy brown shading. Femora pale amber; tibia and tarsus of fore leg with a faint smoky tinge; those of middle and hind legs pale whitish. Wings hyaline, venation pale. Hind wing rather narrow, with two longitudinal veins.

Abdominal tergites 2-10 bright ruddy, with the exception of a narrow pale lateral area; the ruddy color deepening on tergites 7-9, paler on 10. Sternites pale yellowish. Spiracular area marked with a black line, on tergites 2-6. Tails pale. Forceps likewise pale; between the bases of the forceps is a plate with a strongly convex posterior margin.

Female Spinner

Described in Needham et al (1935) as Centroptilum quaesitum

Abdomen of the female is pale yellowish, the anterior tergites with brown posterior margins.

Start a Discussion of Procloeon quaesitum

References

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