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.

I caught several wild and colorful 8-9 inch brook trout in the clear little pool below this waterfall.

From Mystery Creek # 89 in New York

Stream photos

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Hydropsyche (Spotted Sedge) Caddisfly Larva Hydropsyche (Spotted Sedge) Caddisfly Larva

Ventral view of a Hydropsyche (Hydropsychidae) (Spotted Sedge) Caddisfly Larva from the Yakima River in Washington

With a bit of help from the microscope, this specimen keys clearly and unsurprisingly to Hydropsyche.

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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 Labiobaetis dardanus

Where & when

In 4 records from GBIF, adults of this species have been collected during July (50%), June (25%), and October (25%).

In 49 records from GBIF, this species has been collected at elevations ranging from 335 to 7644 ft, with an average (median) of 4741 ft.

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 Baetis dardanus

Body length: 5 mm
Wing length: 5.5 mm

Abdominal tergites 2-6 of male imago hyaline whitish; genitalia of the modified moffati type (now a synonym of Baetis tricaudatus); costal projection of hind wing entirely wanting; hind wing two-veined.

Turbinate eyes are slightly larger than in B. pygmaeus (now a synonym of Acerpenna pygmaea). Thorax dark shiny blackish brown, the lateral sutures marked with whitish. Legs pale yellowish. Wings hyaline. No costal projection near the base of the hind wing. Only two veins present in the hind wing. Abdominal segments 2-6 hyaline whitish; tergites 7-10 brownish olive, the sternites opaque white with brown shading. Faint ruddy shading along the pleural fold. Forceps whitish.

Start a Discussion of Labiobaetis dardanus

References

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