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.

View from atop the permafrost slump

From the Selawik River in Alaska

Stream photos

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Amphizoa Beetle Larva Amphizoa Beetle Larva

Dorsal view of a Amphizoa (Amphizoidae) Beetle Larva from Sears Creek in Washington

This is the first of it's family I've seen, collected from a tiny, fishless stream in the Cascades. The three species of this genus all live in the Northwest and are predators that primarily eat stonefly nymphs Merritt R.W., Cummins, K.W., and Berg, M.B. (2019).

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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 inanum (Tiny Sulphur Duns)

Species Range

source

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 Cloeon inanum

Body length: 6 mm
Wing length: 6.5 mm

Abdominal tergites 2-6 of male imago pale yellowish, with faint ruddy lateral patches.

Turbinate eyes dull orange in dried specimen. Thorax olivaceous brown; the posterior portions and the areas of the wing bases shaded with pale yellowish. Legs pale yellowish; fore femur and tibia with faint smoky tinges. Wings hyaline. Abdominal segments 2-6 semi-hyaline, pale yellowish dorsally; tergites with faint ruddy lateral patches above the spiracular line. Tergites 7-9 bright ruddy brown, 10 pale yellow; sternites pale yellowish. Forceps and tails pale yellowish.

From C. mendax (now a synonym of Procloeon mendax), the only other described species of about the same size, inanum may be distinguished by the yellowish basal abdominal tergites and the olive brown of the thorax.

Start a Discussion of Procloeon inanum

References

Merritt R.W., Cummins, K.W., and Berg, M.B. 2019. An Introduction to the Aquatic Insects of North America (Fifth Edition). Kendall/Hunt Publishing Company.
Needham, James G., Jay R. Traver, and Yin-Chi Hsu. 1935. The Biology of Mayflies. Comstock Publishing Company, Inc.