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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 tilasqua (Yellow Sallies)

Species Range


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

Diagnosis. Isoperla tilasqua male larvae share the typical comma shaped dark pronotal bands common to the Isoperla sobria complex (Fig. 19 b) and have similar numbers of submarginal (A) setae when compared to Isoperla sobria (Table 2). The long, thin apically rounded setae on basal maxillary palpi segments 2 – 3 (Fig. 19 a Inset) are similar to Isoperla baumanni (Fig. 5 e Inset). It is distinct from these species by having a partially light interocellar area connected to the posterior margin of head, a continuous light M shaped band above the anterior ocellus, and a relatively thin median longitudinal light band extending from the anterior ocellus to the light frontoclypeus area (Fig. 19 a).

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 10 – 11 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 connected to light frontoclypeus area by a median longitudinal light band, its width approximately half the posteromedian portion of the light M shaped pattern, lateral thin arms with nearly parallel margins connected to median light band, directed posterolaterally and extending to antennal bases; posterior ocelli with completely enclosed medium sized light areas along outer lateral margins, extending laterally above epicranial suture in fresh specimens; in older preserved specimens, posterior light brown band becomes faded; interocellar area partially light, an irregular shaped light area connected to posterior head capsule by thin light band; occiput with irregular spinulae band extending from below eye to near median epicranial suture, usually enclosed completely by dark to light brown pigment (Fig. 19 a). Lacinia bidentate, total length 978 - 1012 µm (Figs. 2 q, 19 e- h, Tables 2 - 4); submarginal row (A + B) with 4 – 7 setae, groups A-B interrupted by gap below subapical tooth (SAT) inner margin (Fig. 19 g); 2 – 5 submarginal setae (A) in a close set row beginning at the base of the apical tooth (AT), ending before reaching SAT inner margin, plus 1 thin marginal seta (TMS) adjacent to AT inner margin, sometimes obstructed from view by AT, submarginal setae, or broken, and 1 dorsal seta (DS) located below SAT inner margin, partially obstructed by SAT (Figs. 19 g-h); 1 – 3 submarginal setae (B) located past SAT inner margin (Fig. 19 h); 15 – 20 marginal setae (C) initially long-stout and widely spaced, last few shorter and closer, blending into and difficult to differentiate from dorsal surface setae (Fig. 19 e); 36 – 62 ventral surface setae (D) scattered below submarginal and marginal setae, ending posteriorly at approximately ¾ the inner lacinia margin length (Fig. 19 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. 19 f). Galea with 11 – 19 setae in sparse ventral row, apex with 2 – 3 setae. Maxillary Palp segments 2 – 3 with curved, apically rounded setae (Inset, Fig. 19 e). Pronotum with large median light area bordered by thick dark comma shaped bands typical of the Isoperla sobria complex, a range of irregular shaped faded light brown areas usually present between the dark commas and fine dark clothing setae distributed evenly except on a few long light rugosites, lateral margins with broad light bands (Fig. 19 b). Mesonotum and metanotum with contrasting pigment pattern and fine dark clothing setae (Fig. 19 c). Legs with numerous fine golden clothing setae and scattered erect spines on outer surface of femora, erect spines longest and concentrated along dorsal surfaces; fine silky setae sparse on dorsal surface of femora, numerous and continuous on tibia (Fig. 20 q); tibia with faint transverse band near proximal end. Abdominal terga usually with three longitudinal dark stripes; wide light median longitudinal band usually bisected with a median thin faded brown stripe; lateral pair of dark longitudinal stripes about twice as wide as median dark stripe, 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. 19 d).

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

Male. Aedeagus: sclerotized posterior process absent; body with two large posterior lobes and expanded apex, apex deeply inverted, with a pair of small conical lobes at apicolateral margins (Fig. 17 a); one large patch of spinulae concentrated below posteromedian lobe (Fig. 17 b), and a long thin patch along posteroapical margin (Fig. 17 c). 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 first cercal segment, tapering abruptly to blunt apices (Fig. 17 c). Vesicle: rounded lobe, widest at base with broadly rounded apical margin (Fig. 17 d).

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Stonefly Species Isoperla tilasqua (Yellow Sallies)

Species Range
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