Isoperla muir Szczytko & Stewart, 2004

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 : 237-239

Isoperla muir Szczytko & Stewart

( Figs. 2k , 13 a-h, 20 k)

Isoperla muir Szczytko & Stewart 2004 , 130:234-236. ♂, ♀, larva (reared), ovum.

Material examined. TYPE: I. muir Holotype ♂, OR: Douglas Co., Hwy 230, downstream from bridge, Muir Creek , 12/ V/2002, S. Szczytko, K. Stewart (reared with exuviae) ( NMNH); Additional Specimens. OREGON: Douglas Co., Muir Creek, Muir Camp , Hwy 230 bridge, 13.5 mi (21.7 km) E Hwy 138 intersection, 27/V/2008, 31/V/2008 , J. Sandberg, Larvae (reared) .

Male larva. Body length of mature larva 9–13 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 thin and well defined, not connected to light frontoclypeus area, median longitudinal light band absent, lateral thin arms directed posterolaterally, extending to antennal bases; posterior ocelli with completely enclosed small light areas along outer lateral margins; interocellar area entirely dark; occiput with irregular spinulae band extending from below eye to near median epicranial suture, enclosed completely by dark pigment ( Fig. 13a ). Lacinia bidentate, total length 724–837 µm ( Figs. 2k , 13e- h , Tables 2-4 ); submarginal row (A+B) with 7–9 setae, groups A-B interrupted by gap below subapical tooth (SAT) inner margin ( Fig. 13g ); 2 submarginal setae (A) the first inserted at base of apical tooth (AT) inner margin, the second located between AT and SAT inner margins, plus 1 thin marginal seta (TMS) adjacent to AT inner margin, sometimes obstructed from view by AT, submarginal seta (A), or broken, dorsal seta (DS) absent ( Figs 13 g-h); 5–7 submarginal setae (B) located past SAT inner margin ( Fig. 13g ); 9– 11 marginal setae (C), initially long-stout and widely spaced, first marginal setae located under flap-like SAT inner margin ( Fig. 13h – arrow), last few shorter and widely spaced ( Fig. 13e ); 33–58 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. 13f ); dorsal surface setae (DSS) forming dense, laterally protruding, longitudinal band on and along inner-lateral margin, ending at approximately the posterior-most ventral surface setae ( Fig. 13f ). Galea with 22–32 setae in sparse ventral row, apex with 5–6 setae. Maxillary Palp segments 2–3 with nearly straight, apically rounded setae. Pronotum with thin indistinct median light line bordered by irregular dark longitudinal bands with adjacent light rugosites; discs each with brown comma shaped lateral areas, fine dark clothing setae and lateral margins without broad light bands ( Fig. 13b ). Meso and metanotum with contrasting pigment pattern and fine dark clothing setae ( Fig. 13c ). 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 absent on dorsal surface of femora, sparse on tibia ( Fig. 20k ); tibia with very faint transverse bands near proximal end. Abdominal terga with two distinct longitudinal dark stripes; wide light median longitudinal band widest on middle segments, narrowing anteriorly and posteriorly; lateral pair of dark longitudinal stripes extending to lateral margins; numerous fine dark clothing setae and erect spines scattered dorsally; posterior margin with distinct and scattered long, and numerous short spines in a concentrated row ( Fig. 13d ).

Distribution. Oregon, known only from the type location ( Szczytko & Stewart 2004) where it occurs with I. sobria .

Diagnosis. The mature male larvae of I. muir are most similar to I. adunca in that the submarginal row (A+B) setae form a continuous and regularly spaced row ( Figs. 13 g-h). Isoperla muir can be separated from I. adunca by the submarginal setae row (A+B) regularly spaced at about the width of each seta base at points of insertion ( Figs. 13a , g-h), dorsal seta (DS) absent and first marginal seta (C) covered by flap-like subapical tooth inner margin base ( Fig. 13h ).

Remarks. This distinctively pigmented species is rarely collected and is apparently restricted to the type locality. Limited rearing indicated emergence occurred in June.

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. 13a-h. Isoperla muir nymph and ventral maxilla, Muir Creek, Douglas County, OR. Submarginal setae groups A and B, Marginal setae C, Ventral surface setae D, and Dorsal surface setae DSS. White bars = 1 mm, 13e-f 100x, 13g 200x, and 13h 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.