Isoperla tilasqua : Szczytko &amp; Stewart 2004
Creators: name: Sandberg, John B.
Publisher: name: Zenodo
Year: 2011
Subjects: Biodiversity
Taxonomy
Animalia
Arthropoda
Insecta
Plecoptera
Perlodidae
Isoperla
Isoperla tilasqua

description: <i>Isoperla tilasqua</i> Szczytko &amp; Stewart (Figs. 2q, 19 a-h, 20 q) <i>Isoperla tilasqua</i> Szczytko &amp; Stewart 1979, 32:60-61. &amp;male;, &amp;female;, ovum. <i>Isoperla tilasqua</i>: Szczytko &amp; Stewart 2004, 130(2):236- 237. Larva (reared). <b>Material examined.</b> TYPES: <i>I. tilasqua</i> Holotype &amp;male;, Oregon: <b>Benton Co.</b>, Oak Creek, 13-16/ VI/1968,? collector (NMNH #76346); Paratype &amp;female;, Same as Holotype, 7-10/ VI/1968; <b>Additional Specimens.</b> CALIFORNIA: <b>Siskiyou Co</b>., Sacramento River, Headwater, Mt. Shasta, 29/ V/1967, S.G. Jewett Jr., &amp;female; (NMNH); OREGON: <b>Benton Co</b>., Oak Creek, Trap 2, 6.5 mi NW Corvallis, 1 mi N Fish Lab 650 feet, 19- 22/ VI/1968, C. Kerst, &amp;female; (looked more like <i>I. sobria</i>) (NMNH); <b>Clackamas Co</b>., Still Creek, Still Creek Campground, Mt Hood, 10/VI/1955, 17/VI/1967, S.G. Jewett Jr., &amp;female; (NMNH); <b>Grant Co</b>.,?, Trout Meadows, 5500 feet, 09/VII/1967, J. Baker, &amp;female; (NMNH); <b>Umatilla Co</b>., Meacham Creek, Upstream (west) of Hwy 84 bridge, 30/V/2008, 22/V/2011, J. Sandberg, Larvae (reared). <b>Male larva. Body</b> length of mature larva 10–11 mm. <b>Dorsum of head</b> 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. 19a). <b>Lacinia</b> bidentate, total length 978-1012 µm (Figs. 2q, 19e- 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. 19g); 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. 19h); 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. 19e); 36–62 ventral surface setae (D) scattered below submarginal and marginal setae, ending posteriorly at approximately ¾ the inner lacinia margin length (Fig. 19f); dorsal surface setae (DSS) forming dense, laterally protruding, longitudinal band on and along inner-lateral margin, ending before posterior-most ventral surface setae (Fig. 19f). <b>Galea</b> with 11–19 setae in sparse ventral row, apex with 2–3 setae. <b>Maxillary Palp</b> segments 2–3 with curved, apically rounded setae (Inset, Fig. 19e). <b>Pronotum</b> with large median light area bordered by thick dark comma shaped bands typical of the <i>I. sobria</i> 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. 19b). <b>Meso and metanotum</b> with contrasting pigment pattern and fine dark clothing setae (Fig. 19 c). <b>Legs</b> 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. 20q); tibia with faint transverse band near proximal end. <b>Abdominal terga</b> 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. 19d). <b>Distribution.</b> Oregon, Washington. Occurrence in California not confirmed. <b>Diagnosis.</b> <i>Isoperla tilasqua</i> male larvae share the typical comma shaped dark pronotal bands common to the <i>I. sobria</i> complex (Fig. 19b) and have similar numbers of submarginal (A) setae when compared to <i>I. sobria</i> (Table 2). The long, thin apically rounded setae on basal maxillary palpi segments 2–3 (Fig. 19a Inset) are similar to <i>I. baumanni</i> (Fig. 5e 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. 19a). <b>Remarks.</b> The Mt. Shasta <i>I. tilasqua</i> female in the NMNH from California may be the first record for the state. The female western <i>Isoperla</i> taxonomy is known, but variations in the length and shape of the subgenital plate are possible. <i>Isoperla sobria</i> females from California and Oregon had elongate subgenital plates with basolateral margins nearly parallel and rounded apical margins. Eight <i>I. tilasqua</i> females reared from Meacham Creek, Umatilla County, Oregon, all had subgenital plates with median invaginations similar to <i>I. gravitans</i> (Fig. 111 in Szczytko &amp; Stewart, 1979), but the lateral margins, similar to <i>I. sobria</i>, were nearly parallel. A reared or recently field collected male will be required to confirm this interesting and possible range extension.
description: Published as part of <i>Sandberg, John B., 2011, The Isoperla Of California (Plecoptera: Perlodidae); Larval Descriptions And A Key To 17 Western Nearctic Species, pp. 202-258 in Illiesia 7 (22)</i> on pages 253-255, DOI: 10.5281/zenodo.4760320
description: {"references": ["Szczytko, S. W. &amp; K. W. Stewart. 1979. The genus Isoperla (Plecoptera) of western North America; Holomorphology and systematics, and a new", "Szczytko, S. W. &amp; K. W. Stewart. 2004. Isoperla muir, a new species of western Nearctic Isoperla and a new larval description of Isoperla tilasqua Szczytko and Stewart, (Plecoptera: Perlodidae). Transactions of the American Entomological Society, 130 (2): 233 - 243."]}