Artistic view of a Male Pteronarcys californica (Pteronarcyidae) (Giant Salmonfly) Stonefly Adult from the Gallatin River in Montana

Salmonflies
Pteronarcys californica

The giant Salmonflies of the Western mountains are legendary for their proclivity to elicit consistent dry-fly action and ferocious strikes.

Sunlight perfectly strikes the trees at a bend in the Foss River in the Washington Cascades.

From the Foss River in Washington

Stream photos

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Onocosmoecus (Great Late-Summer Sedge) Caddisfly Larva Onocosmoecus (Great Late-Summer Sedge) Caddisfly Larva

Lateral view of a Onocosmoecus (Limnephilidae) (Great Late-Summer Sedge) Caddisfly Larva from the Yakima River in Washington

This specimen keys pretty easily to Onocosmoecus, and it closely resembles a specimen from Alaska which caddis expert Dave Ruiter recognized as this genus. As with that specimen, the only species in the genus documented in this area is Onocosmoecus unicolor, but Dave suggested for that specimen that there might be multiple not-yet-distinguished species under the unicolor umbrella and it would be best to stick with the genus-level ID. I'm doing the same for this one.

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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 Rhithrogena exilis

Where & when

In 1 records from GBIF, adults of this species have been collected during June (100%).

In 1 record from GBIF, this species has been collected at elevation of 1713 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 Dun

Described in Needham et al (1935)

Body length: 6 mm
Wing length: 7 mm

A small pale species; male imago not known, genitalia of subimago seem to be of Rhithrogena anomala type. Male subimago orange-brown; dark marks on pleura above leg bases; mesosternum dark-margined; brown streak runs forward from each side of scutellum; dark marks on each coxa and at each joining of fore leg; median femoral marks as in female.

Female Spinner

Described in Needham et al (1935)

Body length: 6 mm
Wing length: 7 mm

Body of female yellow. Black spot on each side of head, underneath clypeus; black half-ring at base of each antenna. Irregular purplish black lateral marks on pronotum. Faint darker markings on pleura; thoracic sternum unmarked. Legs yellow; a purplish black median spot at center of each femur. Wings semi-hyaline; venation colorless. Abdominal segments 2-6 flushed with pinkish orange; posterior margins of tergites 24 narrowly dull purple. Sternites pale, unmarked. Tails white, unmarked. Female very similar to Rhithrogena uhari, but with paler abdominal tergites. Slightly larger and paler than R. fuscifrons.

Start a Discussion of Rhithrogena exilis

References

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