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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.

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.
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 Siphlonurus marginatus (Gray Drakes)

Species Range

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: 9-10 mm
Wing length: 9 mm

Another medium-sized brownish species with a black mid-ventral line.

Head yellowish brown. No dark band across median carina, but a dark spot beneath each antenna. Thorax bright yellowish brown, the scutella darker. Pleural sclerites dark brown. Fore leg pale brown, tip of tarsus greyish white; femur with indistinct band. Middle and hind legs whitish; joinings brown; femora banded. Wings hyaline; longitudinal veins of fore wing brown, other veins pale yellow or whitish. Costal cross veins indistinct, almost invisible before the bulla; in stigmatic area, tend to anastomose. Stigmatic area, in costal and subcostal spaces, opaque white.

Abdomen olive brown dorsally, pale ventrally. Lateral triangles of tergites dark brown, much reduced in size; oval spots brown. Anterior pale triangles extended to occupy a large part of each tergite. Posterior margins dark brown. Pattern less distinct on apical tergites. Ventrally, a black median line extends continuously from sternites 1 to 9, widened near the posterior margin of each sternite. A small black dot on each side of median line, very near it, at the center of each sternite. Another oblique dark mark anterior to the dark dot, and laterad of it.

Forceps and forceps base yellowish brown. Penes as in fig. 123. Tails yellowish white, joinings dark reddish brown.

Nymph

The nymph has double gills on segments 1 and 2 only. Legs yellowish; middle and hind femora with a brownish band, which is absent from the fore femur. Ventral markings are those of the imago. Usual black band across the tail beyond the middle.


Start a Discussion of Siphlonurus marginatus

References

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

Mayfly Species Siphlonurus marginatus (Gray Drakes)

Taxonomy
Species Range
Common Names
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