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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Limnephilus (Summer Flier Sedge) Caddisfly Larva Limnephilus (Summer Flier Sedge) Caddisfly Larva

Case view of a Limnephilus (Limnephilidae) (Summer Flier Sedge) Caddisfly Larva from the Yakima River 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 fragile (Tiny Sulphur Duns)

Where & when

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

In 2 records from GBIF, this species has been collected at elevations of 1319 and 2070 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 Centroptilum fragile

Body length: 4 mm
Wing length: 5 mm

Abdominal tergites 2-6 of male imago whitish hyaline, slightly brown-tinged, the posterior margins faintly brown.

Turbinate eyes large, narrowly oval, rather kidney-shaped; pale yellow-brown in living insect, bright red in dried specimen. Face yellowish; antennae pale smoky, the bases white. In dried specimen, the face appears dark grey. Thorax shiny blackish brown; pale markings on the scutellum and adjoining areas; pleura brown, with pale markings near the wing bases. Legs white. Wings hyaline. Abdominal segments 2-6 hyaline whitish, slightly tinged with brown, the posterior margins faintly brown; slightly streaked with black, especially in the spiracular area. Tergites 7-10 rather bright brown; sternites opaque white. Second joint of forceps without a conspicuous inward bulge (see fig. 166).

This species may be distinguished from the allied C. ozburni (now a synonym of Procloeon ozburni) by the bright red eyes in dried specimens (blackish brown, in ozburni), and the absence of dark posterior markings on the middle sternites.