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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.

Dorsal view of a Amphizoa (Amphizoidae) Beetle Larva from Sears Creek in Washington
This is the first of it's family I've seen, collected from a tiny, fishless stream in the Cascades. The three species of this genus all live in the Northwest and are predators that primarily eat stonefly nymphs Merritt R.W., Cummins, K.W., and Berg, M.B. (2019).
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.

Stonefly Species Isoperla marmorata (Yellow Sallies)

Species Range


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

Diagnosis. Male larvae of the Isoperla marmorata complex were differentiated from other species with 1 – 2 lacinia submarginal (A) setae by having 41 – 110 ventral surface setae and pronotal discs mostly dark. Within the complex, Isoperla marmorata was distinguished from Isoperla roguensis by usually having the light M shaped pattern connected to the light anterior frontoclypeus area by a light longitudinal band (See also diagnosis under Isoperla fulva). The only exception to the light M shaped pattern character occurred in 8 exuviae collected from Prairie Creek, Humboldt County, California. These possessed partial to entire M shaped light patterns, but were not connected to the light anterior frontal clypeus area.

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 11 – 13 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 indistinct, connected (sometimes partially) to light frontoclypeus area by a wide median longitudinal light band, lateral thin arms directed posterolaterally, extending to antennal bases; posterior ocelli with partially enclosed large light areas along outer lateral margins; interocellar area variable, usually partially light, completely enclosed by dark pigment and not extending past posterior ocelli; occiput with irregular spinulae band extending from below eye to near median epicranial suture, not enclosed completely by dark pigment (Fig. 10 a). Lacinia bidentate, total length 816 – 974 µm (Figs. 2 h, 10 a-h, Tables 2 - 4); submarginal row (A + B) with 2 – 3 setae, groups A-B interrupted by gap below subapical tooth (SAT) inner margin (Fig. 10 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. 10 g-h); 1 – 2 submarginal setae (B) located past SAT inner margin (Fig. 10 h); 7 – 10 marginal setae (C), initially long-stout and widely spaced, last few shorter and variably spaced, blending into and difficult to differentiate from dorsal and ventral surface setae (Fig. 10 e); 72 – 110 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. 10 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. 10 f). Galea with 19 – 40 setae in sparse ventral row, apex with 4 – 5 setae. Maxillary Palp segments 2 – 3 with curved, apically pointed setae. Pronotum with median light area bordered by wide dark bands typical of the Isoperla marmorata complex; discs each with light rugosites concentrated along median dark margins and fine dark clothing setae, lateral margins with broad light bands (Fig. 10 b). Mesonotum and metanotum with contrasting pigment pattern and fine dark clothing setae (Fig. 10 c). Legs with numerous fine golden 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 h); tibia with faint transverse bands near proximal end. Abdominal terga variable, usually with two distinct longitudinal dark stripes; wide light median longitudinal band sometimes bisected with faint, light brown longitudinal stripe; 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. 10 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 with one small posterior lobe, one dorsal lobe and an anterior lobe (Fig. 8 a); one small patch of spinulae concentrated on the inverted membrane above sclerotized process (Figs. 8 a-b); sclerotized process approaching 0.5 mm when fully extended, blade-like in lateral view (Fig. 8 a), distal margin thin in posterior view (Fig. 8 b), 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 gradually to long blunt apices (Fig. 8 c). Vesicle: rounded lobe, widest at base with broadly rounded apical margin (Fig. 8 d).

Start a Discussion of Isoperla marmorata


Stonefly Species Isoperla marmorata (Yellow Sallies)

Species Range
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