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

Where & when

In 2 records from GBIF, adults of this species have been collected during May (50%) and June (50%).

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: 7 mm
Wing length: 7 mm

Head and thorax blackish brown; dark red-brown markings on thoracic pleura. Fore legs yellowish brown; middle and hind legs yellow. Fore leg longer than body. Wings hyaline; longitudinal veins of the costal margin, and apical portions of other longitudinals, yellowish brown. Cross veins almost invisible, except in the stigmatic area, where they are simple, straight and about 17 in number. No cloud in the stigmatic space.

First segments of abdomen very dark reddish brown. Segment 2, the apical two-thirds of segment 7, and segments 8-10, also reddish brown, somewhat paler than the first segment. Segments 3-6, and basal portion of 7, white, semi-hyaline, marked with brown. Posterior margins of these segments widely banded dorsally with reddish to purplish brown. The postero-lateral angles filled with a triangular patch of the same color. Traces of a dark streak on the posterior portion of the median line may be present. Two small dark spots in the pleural fold on each segment, near the anterior and posterior margins. Pleural fold narrowly margined with brown. Mid-ventral ganglionic areas marked with orange-brown.

Forceps base pale brown, forceps pale. Tails yellowish white, joinings faintly darker. The narrow basal joint of the forceps mentioned by Dr. Banks, similar to that of Paraleptophlebia praepedita, seems not to be a true joint. (Sketch 134) The lateral apical processes of the penes are large beak-like structures; no reflexed spurs are present.

Start a Discussion of Neoleptophlebia assimilis


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

Mayfly Species Neoleptophlebia assimilis

Species Range
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