Isoperla sordida Banks, 1906

Sandberg, John B., 2011, The Isoperla Of California (Plecoptera: Perlodidae); Larval Descriptions And A Key To 17 Western Nearctic Species, Illiesia 7 (22), pp. 202-258 : 250-252

Isoperla sordida Banks

( Figs. 2p , 18 a-h, 20 p)

Isoperla sordida Banks 1906, 38 :337.

Holotype ♂, Los Angeles Co., CA, USA.

Isoperla sordida: Szczytko & Stewart 1979 , 32:100-104. ♂, ♀, larva (from ♀ exuviae), ovum.

Material examined. CALIFORNIA: Mono Co., Coldwater Creek, Coldwater Campground , Inyo National Forest , 9000 feet, 16/VIII/1959, C. Alexander, ♂ everted, ♀ ( NMNH) ; Coldwater Campground, Inyo National Forest, 4.7 mi S Mammoth Lakes ( Hwy 203), 26/VII/2010, J. Sandberg, Larvae (reared) ; 08/VIII/2010, ♂ ♀, Larvae (reared); 07/IX/2010, ♂ ♀; 09/VIII/2011, J. Harrington, A. Montalvo, J. Sandberg, Larvae; McKay Creek , ~ 3.6 mi above Sardine Creek, 31/VI/2008, Larvae (ABL) ; Nevada Co., Bog Spring – Sagehen Creek, Near Hobart Mills , 6300 feet, 14/IX/1965, A. Sheldon, ♀ ( NMNH) ; San Bernardino Co.,?, Hurkey Creek Campground, San Jacinto Mts , 4300 feet, 01/VII/1958, C. Alexander, ♂ ♀ (poor condition) ( NMNH) ; OREGON: Deschutes Co., Fall River, Fall River Campground , Hwy 42 (S Century Dr), 13 mi (20.9 km) E Hwy 97, 28& 31/V/2008, J. Sandberg, ♂ ♀, Larvae (reared) ; Linn Co?, McKenzie River, Bridge near Clear Lake , 07/X/1965, S. Jewett Jr., ♀ ( NMNH) ; WASHINGTON:? County,?, Silver Fir Camp, Mt Baker , 1800 feet, 13/VIII/1947, C. Alexander, ♂ ( NMNH) .

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 to light frontoclypeus area by a broad median longitudinal light band, lateral thin arms with nearly parallel margins connected to median light band, directed posterolaterally and extending to antennal bases; posterior ocelli usually with partially enclosed large light areas along outer lateral margins, occasionally light areas small and completely enclosed; interocellar area variable, from completely dark to 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. 18a ). Lacinia bidentate, total length 856–992 µm ( Figs. 2p , 18 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 ( Fig. 18g ); 1 submarginal seta (A) located 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, and 1 dorsal seta (DS) located below SAT inner margin, partially obstructed by SAT or submarginal setae (B) ( Figs. 18 g-h); 2–3 submarginal setae (B) located past SAT inner margin ( Fig 18h ); 8–11 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. 18e ); 41–67 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. 18f ); dorsal surface setae (DSS) forming dense, laterally protruding, longitudinal band on and along inner-lateral margin, ending before posterior-most ventral surface setae ( Fig. 18f ). Galea with 20–26 setae in sparse ventral row, apex with 2–5 setae. Maxillary Palp segments 2–3 with curved, apically pointed setae. Pronotum with light median area bordered by wide dark pigment bands, discs each with large, completely enclosed light areas or “windows”, fine dark clothing setae and lateral margins without broad light bands ( Fig. 18b ). Meso and metanotum with contrasting pigment pattern and fine dark clothing setae ( Fig. 18c ). Legs with numerous fine dark clothing setae and scattered erect spines on outer surface of femora, erect spines longest and concentrated on dorsal surfaces; fine silky setae sparse on dorsal surface of femora, numerous and continuous on tibia ( Fig. 20p ); 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 median longitudinal band; 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. 18d ).

Distribution. Canada: Alberta, British Columbia; USA: Alaska, California, Idaho, Montana, Oregon, and Washington. Only recently confirmed in eastern slope Sierra Nevada streams at elevations greater than 1524 m.

Diagnosis. Isoperla sordida male larvae are distinct among other western Isoperla species with 1–4 submarginal row (A) setae by having a lacinia with 41-67 ventral surface (D) setae ( Figs. 18 e-f), pronotal discs with large distinct window like light areas ( Fig. 18b ), and femora with a sparse row of silky setae ( Fig. 20p ).

Remarks. The type locality for this species is Los Angeles County, California, and is the only specimen of this species known from this county. In Oregon, emergence is in late spring to early summer. In California, emergence occurs in late summer to fall and distribution appears restricted to the eastern Sierra Nevada range high elevation spring fed or snow melt streams above 1524 m.

Figures

Figs. 2a-q. Isoperla lacinia habitus, 40x, Bar = 500µm. 2a. I. acula; 2b. I. adunca; 2c. I. baumanni; 2d. I. bifurcata; 2e. I. denningi; 2f. I. fulva; 2g. I. laucki; 2h. I. marmorata; 2i. I. miwok; 2j. I. mormona; 2k. I. muir; 2L. I. pinta; 2m. I. quinquepunctata; 2n. I. roguensis; 2o. I. sobria; 2p. I. sordida; 2q. I. tilasqua.

Figs. 18a-h. Isoperla sordida nymph and ventral maxilla, Fall River, Deschutes County, OR. Submarginal setae groups A and B, Marginal setae C, Ventral surface setae D, Dorsal seta DS, Dorsal surface setae DSS, and Thin marginal seta TMS. White bars = 1 mm, 18e-f 100x, 18g 200x, and 18h 400x.

Figs. 20a-q. Isoperla front right leg habitus, Larvae, 32–40x, Bar = 1mm. 20a. I. acula; 20b. I. adunca; 20c. I. baumanni; 20d. I. bifurcata; 20e. I. denningi; 20f. I. fulva; 20g. I. laucki; 20h. I. marmorata; 20i. I. miwok; 20j. I. mormona; 20k. I. muir; 20L. I. pinta; 20m. I. quinquepunctata; 20n. I. roguensis; 20o. I. sobria; 20p. I. sordida; 20q. I. tilasqua.