Isoperla pinta Frison

(Figs. 2L, 14 a-h, 20 L)

Isoperla pinta Frison 1937, 21:92.

Holotype ♂, Floras Creek, Curry Co., Oregon.

Isoperla pinta: Szczytko & Stewart 1979, 32:44-49. ♂, ♀, larva (not reared), ovum.

Material examined. CALIFORNIA: Butte Co., Butte Creek, Butte Creek Ecological Reserve, Honey Run Road, 2.9 mi (4.7 km) E intersection with Skyway, 13/I/2007, 05/II/2007, 11/IX/2007, J. Sandberg, Larvae; 17/II/2007, J. Sandberg, Larvae (reared), 04/III/2007, J. Sandberg, D. Pickard, ♂ ♀ Larvae (reared); 07/IV/2007, J. Sandberg, ♂ ♀; 18/I/2008, J. Sandberg, D. Pickard, Larvae; 04/II/2008, J. Sandberg, Larvae; 30/III/2008, ♂ ♀; 27/III/2009, ♂; 03/IV/2009, ♀; 19/II/2010, J. Sandberg, S. Hassur, Larvae (reared); 22/II/2010, J. Sandberg, Larvae (reared); 11/III/2010, J. Sandberg, J. York, Larvae (reared); 14/III/2010, J. Sandberg, Larvae (reared); 27/IV/2010, R. Baumann, B. Kondratieff, J. Sandberg, ♀; El Dorado Co., Cosumnes River, Michigan Bar, 18/IV/1986, R. Bottorff, ♂ ♀ (NMNH); Humboldt Co., Mad River, Arcata Bottoms, Mad River Road, N40.91578° W124.10618° , 10/IV/2010, J. Sandberg, ♂ ♀; Monterey Co.,?, Carmel,, E. VanDuzee , 23/III/1919, ♂ relaxed in KOH (NMNH); Plumas Co., Spanish Creek, Hwy 70 bridge, Quincy Town Park , 10/III/2007, J. Sandberg, Larva; Sacramento Co., Cosumnes River, Sloughhouse , 04/IV/1982, 25/V/1982, R. Bottorff, ♀ (NMNH); Tulare Co., Lemon Creek, Near Los Angeles, 14/IV/1950, R. Usinger, ♂ ♀ (NMNH); OREGON: Benton Co.,?, Corvallis, 06/IV/1907, J. Bridwell, ♂ (NMNH); Clatsop Co., Nehalem River, at Red Bluff Road 4 mi (6.4 km) NE Elsie , 17- 18/IV/1965, S. Jewett Jr., ♀ (NMNH); Curry Co., Rogue River, Orchard Bar, Cty Hwy 595 (Agness Rd) , 8.9 mi (14.3 km)NE Hwy 101, 14/II/2010, J. Sandberg, ♀, Exuviae; Rogue River, Coyote Bar, Cty Hwy 595 (Agness Rd), 5.6 mi (9.0 km) NE Hwy 101, 27/II/2010, J. Sandberg, Larvae; Douglas Co., Cow Creek, at Quines Creek, 08/IV/1968, S. Jewett Jr ., ♀ (NMNH); Josephine Co ?., Applegate River, Location?, 23/II/1968, S. Jewett Jr ., ♀ (NMNH); Marion Co., Santiam River, Near Jefferson, 11/IV/1967, S. Jewett Jr ., ♀ (NMNH). Santiam River, Boat Launch & Rest Stop, I-5 bridge, 17 mi (27.3 km) S Salem, 19/III/2007, J. Sandberg, D. Pickard, J. Slusark , ♂.

Male larva. Body length of mature larva 10–13 mm. Dorsum of head with contrasting pigment pattern and fine light and dark clothing setae, anterior frontoclypeus margin unpigmented; light M shaped pattern anterior to median ocellus not typical of western Isoperla species, usually connected to light frontoclypeus area by thin median longitudinal light band, lateral arms distinctly swollen at approximately mid length, usually directed laterally, extending to above antennal bases; posterior ocelli with partially enclosed large light areas along outer lateral margins; interocellar area partially light, an irregular shape enclosed by dark brown pigment anteriorly and light brown pigment posteriorly; occiput with irregular spinulae band extending from below eye to near median epicranial suture, not enclosed completely by dark pigment (Fig. 14a). Lacinia bidentate, total length 682–841 µm (Figs. 2L, 14 e-h, Tables 2-4); submarginal row (A+B) with 4–5 setae, groups A-B interrupted by gap below subapical tooth (SAT) inner margin (Figs. 14 g-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, first seta half as stout at base as marginal setae (C) and longitudinal striations weak or absent, all other species first seta nearly as stout and with striations, 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, partially obstructed by SAT or first submarginal setae (B) (Figs. 14 g-h); 2–3 submarginal setae (B) located past SAT inner margin (Fig. 14h); 4– 7 marginal setae (C), initially long-stout and widely spaced, last few shorter and variably spaced, blending into and difficult to differentiate from dorsal setae (Fig. 14e); 29–50 ventral surface setae (D) forming dense longitudinal band below marginal setae, ending posteriorly at approximately ¾ the inner lacinia margin length, and concentrated in posterior half (Fig. 14f); dorsal surface setae (DSS) forming dense, laterally protruding, longitudinal band on and along inner-lateral margin, ending before posterior-most ventral surface setae (Fig. 14f). Galea with 8–17 setae in sparse ventral row, apex with 4 setae. Maxillary Palp segments 2–3 with curved, apically rounded setae. Pronotum with irregular shaped median light area bordered by complex pattern of dark markings; discs each with distinctive lateral dark checkerboard pattern, fine dark and light clothing setae and lateral margins with broad light bands (Fig. 14b). Meso and metanotum with contrasting pigment pattern and fine dark and light clothing setae (Fig. 14c). Legs with numerous light and dark clothing setae and scattered erect spines on outer surface of femora, erect spines longest and concentrated along dorsal surface; fine silky setae numerous and continuous on dorsal surfaces of femora and tibia (Fig. 20L); distal femur and proximal tibia with transverse bands. Abdominal terga with three distinct longitudinal stripes and small dark spots arranged in pairs on dorsal surface and in triplets laterally; wide light median longitudinal band bisected with irregular shaped dark median stripe; lateral pair of dark longitudinal stripes about as wide as median dark stripe, not extending to lateral margins; numerous fine light clothing setae and erect spines scattered dorsally; posterior margin with scattered long and numerous short spines in a concentrated row (Fig. 14d).

Distribution. Canada: British Columbia, Alberta; USA: California, Colorado, Idaho, Montana, Oregon, Utah, Washington, and Wyoming. Mexico: Baja California. Widely distributed throughout northern California.

Diagnosis. The male larvae of I. pinta are distinct among other western Isoperla species with 2–4 submarginal setae (A+B). The 1–2 submarginal setae (A) are less than half as stout at their base than the largest marginal setae (C) and lack or possess weak longitudinal striations (Figs. 14 g-h).

Remarks. The distinctive head and pronotal pigment pattern of larvae could be used alone to identify individuals of this species in California, where Isoperla phalerata Needham has not been collected. In Butte Creek, Butte County, it was the first of three Isoperla species to emerge in March–April.

Specimens examined in this study were compared with I. phalerata from previous drumming studies (Sandberg 2011, Sandberg & Stewart 2006), and the adults, larvae and drumming characters could not be separated. Perhaps these are sibling species and can only be separated by very slight aedeagus character differences or Scanning Electron Microscope characters of the ovum (Szczytko & Stewart 1979 – Figs. 64-71). However, it seems likely the Colorado I. phalerata population studied in Sandberg & Stewart (2006) was actually I. pinta . Further study is needed to confirm the identity of these two very closely related species.