Header image
Enter a name
Lateral view of a Male Baetis (Baetidae) (Blue-Winged Olive) Mayfly Dun from Mystery Creek #43 in New York
Blue-winged Olives

Tiny Baetis mayflies are perhaps the most commonly encountered and imitated by anglers on all American trout streams due to their great abundance, widespread distribution, and trout-friendly emergence habits.

Dorsal view of a Glossosoma (Glossosomatidae) (Little Brown Short-horned Sedge) Caddisfly Larva from the Yakima River in Washington
I caught this tiny larva without a case, but it seems to key pretty clearly to to Glossosomatidae. From there, the lack of sclerites on the mesonotum points to either Glossosoma or Anagapetus. Although it's difficult to see in a 2D image from the microscope, it's pretty clear in the live 3D view that the pronotum is only excised about 1/3 of its length to accommodate the forecoxa, not 2/3, which points to Glossosoma at Couplet 5 of the Key to Genera of Glossosomatidae Larvae.
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 quinquepunctata (Little Yellow Stoneflies)

This species is often the most common Perlodidae or Little Yellow Stone In Northern California, especially in mid-elevation rivers and streams.

Where & when

Time of year : Early spring through late Summer depending on elevation

Preferred waters: Riffles and runs over cobble

In 23 records from GBIF, adults of this species have been collected during June (48%), July (43%), and May (9%).

In 4 records from GBIF, this species has been collected at elevations of 4403, 7920, 8760, and 8862 ft.

Species Range


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

Diagnosis. Mature male Isoperla quinquepunctata larval pigment patterns are most similar to Isoperla acula, Isoperla mormona and Isoperla sordida (Figs. 3 a-d, 12 a-d, 15 a-d, 18 a- d). In California, this species can be differentiated from other species with 1 – 4 submarginal setae (A + B) by having 48 – 97 ventral surface (D) setae (Figs. 15 eh), pronotal discs patterned with small to large central light areas, when large these areas not completely enclosed by dark pigment (Fig. 15 b).

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 a mixture of fine light and dark clothing setae, anterior frontoclypeus margin unpigmented; light M shaped pattern anterior to median ocellus usually indistinct, not connected to light frontoclypeus area, median light longitudinal light band absent, lateral thin arms faint, directed posterolaterally, extending to antennal bases; posterior ocelli with partially enclosed large light areas along outer lateral margins; interocellar area partially light and variable, either completely enclosed by dark pigment and entirely within the triangle, enclosed by dark pigment and extended posteromedially past posterior ocelli, or connected to posterior margin of head by thin longitudinal light pigment band; occiput with irregular spinulae band extending from below eye to near median epicranial suture, not enclosed completely by dark pigment (Fig. 15 a). Lacinia bidentate, total length 696 – 828 µm (Figs. 2 m, 15 e- h, Tables 2 - 4); submarginal row (A + B) with 3 – 4 setae, groups A-B interrupted by gap below subapical tooth (SAT) inner margin (Figs. 15 g-h); 1 submarginal seta (A) inserted at the base apical tooth (AT) inner margin, plus 1 thin marginal seta (TMS) adjacent to AT inner margin, sometimes obstructed from view by AT or broken, and 1 dorsal seta (DS) located below SAT inner margin, partially obstructed by SAT (Figs. 15 g-h); 2 – 3 submarginal setae (B) located past SAT inner margin (Fig. 15 h); 7 – 11 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. 15 e); 48 – 97 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. 15 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. 15 f). Galea with 23 – 27 setae in sparse ventral row, apex with 5 setae. Maxillary Palp segments 2 – 3 with curved, apically pointed setae. Pronotum with median light area occasionally with a short central indistinct brown band bordered by irregular dark pigment markings; discs each with partially to completely enclosed light areas, the largest resembling the “ windows ” described for Isoperla acula, fine dark clothing setae and lateral margins with broad light bands (Fig. 15 b). Mesonotum and metanotum with contrasting pigment pattern and fine light and dark clothing setae, dark setae enclosed by dark pigment (Fig. 15 c). Legs with numerous fine light clothing setae and scattered erect spines on outer surface of femora, erect spines longest and concentrated on dorsal surfaces; fine silky setae numerous and continuous on dorsal surfaces of femora and tibia (Fig. 20 m); tibia with at most, a very faint and incomplete band near joint with femora; femora with median, longitudinal light brown pigment band concentrated distally. Abdominal terga with three distinct longitudinal dark stripes; wide light median longitudinal band bisected with variable, thin to thick, dark median longitudinal stripe; lateral pair of dark longitudinal stripes about twice as wide as median dark stripe, nearly 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. 15 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 of aedeagus with a small posteromedian lobe covered with minute spinulae, one posteroapical lobe, one dorsal lobe, and an anterior lobe (Fig. 12 a). Posterolateral margin of ninth and tenth terga with patches of long stout setae, fewer and smaller on tergum ten (Fig. 12 c). 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 blunt apices (Fig. 12 c). Vesicle: rounded lobe, widest at base with broadly rounded apical margin (Fig. 12 d), sometimes appears constricted along inner sclerotized lateral margins with wider and broadly rounded membranous outer lateral margins.

Specimens of the Stonefly Species Isoperla quinquepunctata

2 Nymphs

Start a Discussion of Isoperla quinquepunctata

Stonefly Species Isoperla quinquepunctata (Little Yellow Stoneflies)

Species Range
Troutnut.com is copyright © 2004-2024 (email Jason). privacy policy