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.

Cedar sweepers line the fertile spring creek headwaters of a famous trout stream.

From the Bois Brule River in Wisconsin

Stream photos

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Limnephilidae (Giant Sedges) Caddisfly Larva Limnephilidae (Giant Sedges) Caddisfly Larva

Dorsal view of a Limnephilidae (Giant Sedges) Caddisfly Larva from the Yakima River in Washington

This specimen resembled several others of around the same size and perhaps the same species, which were pretty common in my February sample from the upper Yakima. Unfortunately, I misplaced the specimen before I could get it under a microscope for a definitive ID.

10 Recently Added Photos

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 Callibaetis pretiosus (Speckled Duns)

This uncommon species may be locally abundant.

Where & when

In 9 records from GBIF, adults of this species have been collected during August (44%), May (22%), July (22%), and September (11%).

In 2 records from GBIF, this species has been collected at elevations of 20 and 72 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.

Female Spinner

Described in Needham et al (1935)

Body length: ? mm
Wing length: 6.5 mm

A brown species; cross veins of fore wing rather numerous; marginal intercalaries occur singly; male not known.

Body of female brown. Two narrow white stripes on the thoracic notum. Legs pale, tips of tibiae dark, also the tarsal joints. Wings hyaline; veins and cross veins mostly white, but the longitudinal veins with some dark marks. Costal vitta consists of a “fairly broad brown stripe from base to tip, its hind margin sinuate with four projections, four hyaline spots in the subcostal area before the middle, about five pale spots on costal margin before the middle, and several more or less connected beyond.” Along the hind margin are five or six faint irregular clouds. Hind wing much as in Callibaetis floridanus. Abdomen brown, with darker spots on the sides.

Start a Discussion of Callibaetis pretiosus

References

Knopp, Malcolm and Robert Cormier. 1997. Mayflies: An Angler's Study of Trout Water Ephemeroptera . The Lyons Press.
Needham, James G., Jay R. Traver, and Yin-Chi Hsu. 1935. The Biology of Mayflies. Comstock Publishing Company, Inc.