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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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Stonefly Species Isoperla roguensis (Yellow Sallies)

Species Range


Source: The Isoperla Of California (Plecoptera: Perlodidae); Larval Descriptions And A Key To 17 Western Nearctic Species

Diagnosis. Mature male larvae of Isoperla roguensis are most similar to Isoperla fulva and Isoperla marmorata. The larvae of this species can not be separated from Isoperla fulva but can be distinguished from Isoperla marmorata by the lack of or reduced M shaped light pattern not connected to unpigmented frontoclypeus (Fig. 16 a). Pigment patterns are known to vary in Isoperla and a nonpigment character must be found before increased species resolution can be achieved in the Isoperla marmorata complex.

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.

Source: The Isoperla Of California (Plecoptera: Perlodidae); Larval Descriptions And A Key To 17 Western Nearctic Species

Male larva. Body length of mature larva 9 – 12 mm. Dorsum of head with contrasting pigment pattern and fine dark clothing setae, anterior frontoclypeus margin unpigmented; light M shaped pattern anterior to median ocellus variable, usually indistinct, not connected to light frontoclypeus area and completely enclosed in dark pigment, median longitudinal light band absent, lateral thin arms faint, lacking clothing setae, directed posterolaterally and extending to antennal bases; posterior ocelli with partially enclosed large light areas along outer lateral margins; interocellar area variable, from completely dark to partially light, when small light area present, completely enclosed by dark pigment and not extending posteriorly past posterior ocelli; occiput with irregular spinulae band extending from below eye to near median epicranial suture, not enclosed completely by dark pigment (Fig. 16 a). Lacinia bidentate, total length 682 – 862 µm (Figs. 2 n, 16 e- h, Tables 2 - 4); submarginal row (A + B) with 3 setae, groups A-B interrupted by gap below subapical tooth (SAT) inner margin (Fig. 16 g); 1 submarginal seta (A) inserted at base of apical tooth (AT) inner margin, plus 1 thin marginal seta (TMS) adjacent to AT inner margin, sometimes obstructed from view by AT, submarginal seta (A) or broken, and 1 dorsal seta (DS) located below SAT inner margin, partially obstructed by SAT or submarginal setae (B) (Figs. 16 g-h); 2 submarginal setae (B) located past SAT inner margin (Fig. 16 h); 5 – 9 marginal setae (C), initially long-stout and widely spaced, last few shorter and widely spaced, blending into and difficult to differentiate from dorsal and ventral surface setae (Fig. 16 e); 48 – 88 ventral surface setae (D) forming dense longitudinal band below submarginal and marginal setae, ending posteriorly at approximately ¾ the inner lacinia margin length, setae closest to inner margin protrude laterally past lacinia margin (Fig. 16 f); dorsal surface setae (DSS) forming dense, laterally protruding, longitudinal band on and along inner-lateral margin, ending before posterior-most ventral surface setae (Fig. 16 f). Galea with 19 – 27 setae in sparse ventral row, apex with 4 – 6 setae. Maxillary Palp segments 2 – 3 with curved, apically pointed setae. Pronotum with median light area occasionally with a thin central indistinct brown band bordered by wide dark irregular pigment bands typical of the Isoperla marmorata group; discs each with variable and irregular inner lateral dark pigment margins, variable light rugosites usually concentrated along inner dark band margins, fine dark clothing setae except over rugosites and lateral margins with broad light bands (Fig. 16 b). Mesonotum and metanotum with contrasting pigment pattern and fine dark clothing setae (Fig. 16 c). Legs with numerous fine golden to light brown clothing setae and scattered erect spines on outer surface of femora, erect spines longest and concentrated on dorsal surface; fine silky setae sparse on dorsal surface of femora, numerous and continuous on tibia (Fig. 20 n); tibia with extremely faint transverse bands near proximal end. Abdominal terga variable, usually with two distinct longitudinal dark stripes; wide light median longitudinal band sometimes bisected by faint, light brown longitudinal median band; lateral pair of dark longitudinal stripes usually not extending to lateral margins; numerous fine dark clothing setae and erect spines scattered dorsally; posterior margin with scattered long and numerous short spines in a concentrated row (Fig. 16 d).

Source: The Isoperla Of California (Plecoptera: Perlodidae); Updated Male Descriptions And Adult Keys For 18 Western Nearctic Species

Male. Aedeagus: sclerotized posterior process present; body of aedeagus with one posterior lobe, one large dorsal lobe, and one anterior lobe (Fig. 14 a); one bulbous and usually bi-hemispherical shaped patch of spinulae above sclerotized process and a small pair of spinule patches placed laterally (Figs. 14 a-c); sclerotized process length approaching 0.5 mm, blade-like in lateral view (Fig. 14 a), distal margin expanded and slightly membranous in posterior view (Fig. 14 b), shape of distal expanded margin variable, and narrow proximal portion of sclerotized process usually inverted inside posterior aedeagal membrane. Abdominal terga 8 - 9, 9, 9 - 10: without stout spinulae or long stout setae. Posterolateral margins of at least abdominal segment 8 with scale-like setae clustered in brushes of several setae. Paraprocts: curved dorsally, length if straightened subequal to combined first and second cercal segments, tapering abruptly to tiny sharp apices (Fig. 14 c). Vesicle: rounded lobe, widest at base with broadly rounded apical margin (Fig. 14 d).

Start a Discussion of Isoperla roguensis

Stonefly Species Isoperla roguensis (Yellow Sallies)

Species Range
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