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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.

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.
Troutnut is a project started in 2003 by salmonid ecologist Jason "Troutnut" Neuswanger to help anglers and fly tyers unabashedly embrace the entomological side of the sport. Learn more about Troutnut or support the project for an enhanced experience here.

Mayfly Species Siphlonurus quebecensis (Gray Drakes)

This is the Siphlonurus species I have encountered most frequently on Eastern trout waters. I often find its spinners swarming in a mix with Siphlonurus alternatus, and I have read that Siphlonurus rapidus may join these groups as well.

Where & when

Time of year : Mid-May through late July

In 23 records from GBIF, adults of this species have mostly been collected during June (78%) and May (13%).

In 1 record from GBIF, this species has been collected at elevation of 942 ft.

Species Range

Spinner behavior

Time of day: Dusk

Habitat: Riffles

I have had nothing but frustration when these spinners are over the water. They are present on almost every summer evening at certain riffles on a favorite river, usually in swarms large enough to tease the angler but too small to cause a good rise of trout. I have only seen the trout respond well to their fall once, maybe, in a freak series of hungry rises that ended faster than I could get in position to cast. Yet others have reported good fishing to this species on that very river, and they are even more popular to the East in Michigan.

They are large mayflies with the qualities trout enjoy, so pay close attention when you spot their swarms, but beware their reputation for disappointment.

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

Body length: 11-13 mm
Wing length: 12-13 mm

A handsome dark species, with more or less complete dark ventral U-shaped marks.

Head yellowish. Compound eyes purplish grey. Thorax reddish brown; pinkish markings on mesonota and metanota; sutures of pleura widely cream colored. Fore leg of male light reddish brown. Femur with a dark ring at basal joining, and a brown band near apex; apex yellowish. Tibia and tarsus concolorous, brown. Middle and hind legs yellowish; base of femur, apical femoral band, knee and joinings of other segments brown. Last three tarsal joints, and claws, washed with brown.

Wings hyaline. Veins dark purplish brown, except stigmatic cross veins, which are pale brown, almost obsolete along the subcosta. Stigmatic area opaque white. Stigmatic cross veins numerous, anastomosing at the middle of their length. A thickened spot at the bulla, on subcosta, radius and radial sector.

Abdomen dark reddish brown dorsally, with usual pale lateral triangles and dark oval marks. Tergites 8-10 brighter red in color, and with larger pale areas, which are often powdery white. Ventrally whitish, subhyaline. Each sternite typically has the usual dark lateral patches and oblique dark streaks, the latter joined at the anterior margin to form the U-shaped dark mark. Sternites 1-7 pale in the median area, on the posterior margin and the antero-lateral angle. Sternites 8 and 9 largely dark except for a pale median streak in the posterior half. Genitalia pale reddish brown. Penes distinctive in form (see fig. 123). Tails pale yellowish white. Each joining rather widely ringed with purplish brown.

Nymph

Nymphs have double gills on segments 1 and 2 only. Femur banded near the apex, as in the imago. Tibia with a basal band, tarsus twice banded. Ventral pattern of the abdomen comparable to that of the imago. A wide black band across the tails at about 2/3 of their length.

Specimens of the Mayfly Species Siphlonurus quebecensis

1 Female Dun
1 Male Spinner
1 Female Spinner
4 Nymphs

Start a Discussion of Siphlonurus quebecensis

References

Mayfly Species Siphlonurus quebecensis (Gray Drakes)

Taxonomy
Species Range
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