Isoperla marmorata Needham & Claassen, 1925

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 : 229-230

Isoperla marmorata Needham & Claassen

( Figs. 2h , 10 a-h, 20 h)

Clioperla marmorata Needham & Claassen 1925 , 2:142.

Holotype ♀, Reno , Washoe Co., Nevada .

Isoperla marmorata: Szczytko & Stewart 1979 , 32:62-67. ♂, ♀, larva (reared), ovum.

Material examined. CALIFORNIA: Butte Co.,?, 9 mi (14.5 km) N Oroville, 24/IV/1955, S. Hitchcock, Larvae ( NMNH);?, Chico, 23/IV/1923, E. VanDuzee, ♂ ( NMNH); Big Chico Creek, CSU-Chico near Holt Hall, 29/III/2007, 08/IV/2008, J. Sandberg, ♂ ♀; Big Chico Creek, Five-Mile Recreation Area, Centennial Ave. & Crow Canyon Ct., 27/III/2010, J. Sandberg, Larvae (reared); Butte Creek, 400 meters upstream from Doe Mill Road bridge, 28/V/2006, J. Sandberg, D. Pickard, Larvae (reared); Butte Creek, Butte Creek Ecological Reserve, Honey Run Rd., 2.9 mi (4.7 km) E intersection with Skyway, 11/III/2010, J. Sandberg, J. York, Larvae (reared); Mud Creek, Richardson Springs, 15/IV/2010, J. Sandberg, D. Pickard, J. York, Larvae (reared); Contra Costa Co.,?, near Moraga, 26/IV/1966, D. Denning, ♀ (poor condition) ( NMNH); El Dorado Co., Deadman Creek, Church Mine Rd. crossing, 2.45 mi (3.9 km) SE El Dorado, 05/IV/2009, J. Sandberg, A. Richards, Larvae (reared); Greenwood Creek, Greenwood Creek Park, Hwy 49, 4 mi (6.4 km) E Pilot Hill, 28/III/2009, 11/IV/2009, J. Sandberg, Larvae (reared); Martinez Creek, Martinez Creek Rd., 3.5 mi (5.6 km) SE El Dorado, 04/IV/2009, J. Sandberg, D. Pickard, Larvae (reared); NF Cosumnes River, Hwy 49 Nashville, 31/V/1982, R. Bottorff, ♀ ( NMNH); NF Cosumnes River, Hwy 49 cattle corral, 1.7 mi (2.7 km) S Nashville below confluence with MF Cosumnes River, 28/IV/2007, 28/III/2009, 30/III/2009, 11/IV/2009; J. Sandberg, 05/IV/2009; J. Sandberg, A. Richards, 11/IV/2009; J. Sandberg, Larvae (reared); Weber Creek, Forni Road bridge crossing at Placerville, 28/III/2009, J. Sandberg, Larvae (reared); Humboldt Co., Mad River, Arcata Bottoms, Mad River Rd., N40.91578º W124.10618°, 10/IV/2010, J. Sandberg, ♀; Nevada Co., Sagehen Creek, at diversion structure, 6300 feet, 18/VI/1965, A. Sheldon, ♀ ( NMNH); Placer Co., Secret Ravine, Rocklin Road bridge crossing at Rocklin, 11/IV/2008, J. Sandberg, A. Richards, Larva; Plumas Co., Domingo Spring, Domingo Springs Campground, 8.5 mi (13.7 km) NW Chester on Old Red Bluff Rd., 13/VI/2007, 03/VII/2010, J. Sandberg, ♂ ♀; Sacramento Co., Cosumnes River, Michigan Bar, 23/IV/1982, R. Bottorff, Exuviae ( NMNH); Cosumnes River, Michigan Bar, 18/IV/1986, R. Bottorff, ♂ ♀ damaged ( NMNH); Siskiyou Co., McCloud River, Middle Falls near Fowlers Campground, 5.5 mi (8.8 km) E McCloud (Hwy 89), 13/V/2007, J. Sandberg, D. Pickard, ♂; Tehama Co., Big Chico Creek, Hwy 32 bridge, 2.3 mi (3.7 km) N of Lomo & Humboldt Rd. intersection, 06/I/2007, J. Sandberg, A. Richards, Larva; 03/IV/2010, J. Sandberg, Larvae (reared dark variant); Pine Creek, Wurlitzer Ranch, Barber Rd., 1.5 mi (2.4 km) E Meridian Rd. intersection, 07/III/2007, 03/III/2008, 03/III/2010, J. Sandberg, D. Pickard, Larvae (reared); SF Calf Creek, Hwy 32 crossing, 2.75 mi (4.4 km) S Potato Patch Campground, 26/IV/2010, R. Baumann, B. Kondratieff, A. Richards, J. Sandberg, J. Slusark, Larvae (reared); Trinity Co., SF Trinity River, Hwy 36, Forest Glen Campground, Forest Glen, J. Sandberg, 22/V/2008, Exuviae. OREGON: Benton Co., Rock Creek, 4 mi (6.4 km) W Philomath, 27/IV/1963, T. Schuh, ♀ ( NMNH); Clatsop Co., Nehalem River, at Red Bluff Rd., 4 mi (6.4 km) NE Elsie, 17-18/IV/1965, S. Jewett Jr., ♂ ( NMNH); Columbia Co., Scappoose Creek,?location, 08/V/1948, S. Jewett Jr., ♀ ( NMNH); Jackson Co,. Squaw Lake,?location, 22/V/1964, J. Schuh, ♂ ( NMNH); Linn Co., Stream near CAP. III, Monument Peak, 16/VII/1960,?collector, ♀ ( 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 (sometimes partially) to light frontoclypeus area by a wide 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 variable, usually 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. 10a ). Lacinia bidentate, total length 816–974 µm ( Figs. 2h , 10 a-h, Tables 2-4 ); submarginal row (A+B) with 2–3 setae, groups A-B interrupted by gap below subapical tooth (SAT) inner margin ( Fig. 10g ); 1 submarginal seta (A) inserted 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, submarginal seta (A) or broken, and 1 dorsal seta (DS) located below SAT inner margin, partially obstructed by SAT or submarginal setae (B) ( Figs. 10 g-h); 1–2 submarginal setae (B) located past SAT inner margin ( Fig. 10h ); 7–10 marginal setae (C), initially long-stout and widely spaced, last few shorter and variably spaced, blending into and difficult to differentiate from dorsal and ventral surface setae ( Fig. 10e ); 72–110 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. 10f ); dorsal surface setae (DSS) forming dense, laterally protruding, longitudinal band on and along inner-lateral margin, ending before posterior-most ventral surface setae ( Fig. 10f ). Galea with 19–40 setae in sparse ventral row, apex with 4–5 setae. Maxillary Palp segments 2–3 with curved, apically pointed setae. Pronotum with median light area bordered by wide dark bands typical of the I. marmorata complex; discs each with light rugosites concentrated along median dark margins and fine dark clothing setae, lateral margins with broad light bands ( Fig. 10b ). Meso and metanotum with contrasting pigment pattern and fine dark clothing setae ( Fig. 10c ). Legs with numerous fine golden clothing setae and scattered erect spines on outer surface of femora, erect spines longest and concentrated on dorsal surface; fine silky setae sparse on dorsal surface of femora, numerous and continuous on tibia ( Fig. 20h ); 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 longitudinal stripe; 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. 10d ).

Distribution. California, Nevada, Oregon, and Washington. In northern California, this species was found in small to medium sized creeks and rivers at a variety of elevations. It occurred with I. acula , I. mormona , Isoperla pinta Frison , Isoperla quinquepunctata (Banks) , and I. roguensis .

Diagnosis. Male larvae of the I. marmorata complex were differentiated from other species with 1–2 lacinia submarginal (A) setae by having 41–110 ventral surface setae and pronotal discs mostly dark. Within the complex, I. marmorata was distinguished from I. roguensis by usually having the light M shaped pattern connected to the light anterior frontoclypeus area by a light longitudinal band (See also diagnosis under I. fulva ). The only exception to the light M shaped pattern character occurred in 8 exuviae collected from Prairie Creek, Humboldt County, California. These possessed partial to entire M shaped light patterns, but were not connected to the light anterior frontal clypeus area.

Remarks. In Big Chico Creek, this species was collected at 82.9 m elevation, at Five-mile Recreation Area, Chico, and at 1043.9 m elevation at the Hwy 32 crossing, 45.1 km north of Chico. The adults of these two locations had different pigment patterns; the low elevation population was lighter than the high elevation darker population. A black adult I. marmorata variant has also been collected from Prairie Creek, Humboldt County (J.J. Lee, pers. com.). These “dark and black” variant color morphs have been suggested to be either ecophenotypes or cryptic sibling species within I. marmorata and more studies are needed to address this observation. Emergence occurred in April–May and the black Prairie Creek, Humboldt County population began its emergence in March (J.J. Lee, pers. com.).

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. 10a-h. Isoperla marmorata nymph and ventral maxilla, Greenwood Creek, El Dorado County, CA. Submarginal setae groups A and B, Marginal setae C, Ventral surface setae D, Dorsal surface setae DSS, and Dorsal seta DS. White bars = 1 mm, 10e-f 100x, 10g 200x, and 10h 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.