Stonefly Species Isoperla acula (Yellow Sallies)

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 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 partially light and generally diamond shaped, completely enclosed by dark pigment, light area extending past posterior ocelli, reaching dark pigment below the arms of the epicranial suture; occiput with irregular spinulae band extending from below eye to near median epicranial suture, not enclosed completely by dark pigment (Fig. 3 a). Lacinia bidentate, total length 687 – 786 µm (Fig. 2 a, 3 e- h, Tables 2 - 4); submarginal row (A + B) with 4 setae, groups A-B interrupted by gap below subapical tooth (SAT) inner margin (Fig. 3 h); 1 – 2 submarginal setae (A), the first inserted at base of apical tooth (AT) inner margin, the second when present, located between AT and SAT inner margins, 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 sometimes obstructed by SAT (Figs. 3 g-h); 2 – 3 submarginal setae (B) located past SAT inner margin (Figs 3 g-h); 7 – 9 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. 3 e); 28 – 41 ventral surface setae (D) scattered below submarginal and marginal setae, ending posteriorly at approximately ¾ the inner lacinia margin length (Fig. 3 f); dorsal surface setae (DSS) continue from last marginal seta (C) as a single, laterally protruding, submarginal row along inner-lateral margin, ending before posterior-most ventral surface setae (Fig. 3 f). Galea with 42 – 61 setae in thick ventral band, apex with 4 – 5 setae. Maxillary Palp segments 2 – 3 with curved, apically pointed setae. Pronotum with median light area bordered (at least partially) by thin, irregular dark bands; discs each with partially to totally enclosed light areas or “ windows ” and fine dark clothing setae, lateral margins with broad light bands (Fig. 3 b). Mesonotum and metanotum with contrasting pigment pattern and fine dark clothing setae (Fig. 3 c). Legs with numerous fine dark clothing setae and scattered erect spines on outer surface of femora, erect spines longest and concentrated along dorsal surfaces; fine silky setae numerous and continuous on dorsal surfaces of femora and tibia (Fig. 20 a); tibia with faint transverse bands near proximal end. Abdominal terga with three distinct longitudinal dark stripes; wide light median longitudinal band bisected with thin dark median longitudinal stripe; lateral pair of dark longitudinal stripes about twice as wide as median dark stripe, 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. 3 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 a long recurved tube without major lobes, tapering to a multi-lobed apex (Fig. 1 a); a pair of long, nearly parallel patches of fine spinulae along posteroapical margin (Figs. 1 a-b). Ninth tergum with mesoposterior bipartite to oval patches of stout dark spinulae and long fine scattered setae, tenth tergum with only a few small spinulae (Fig. 1 c). Posterolateral margins of at least abdominal segment 8 with scale-like setae clustered in brushes of several setae (Fig. 1 d inset). Paraprocts: curved dorsally, length if straightened longer than combined first and second cercal segments, tapering gradually to long sharp apices (Fig. 1 c). Vesicle: rectangular, length half as long as wide (Fig. 1 d).