Sweltsa oregonensis (Frison)

Nye, Kelly C. & Stark, Bill P., 2010, A Scanning Electron Microscopy Study Of The Epiprocts Of Western North American Sweltsa (Plecoptera: Chloroperlidae), Illiesia 6 (18), pp. 248-255 : 250

Sweltsa oregonensis (Frison)

( Figs. 1-6 )

Alloperla oregonensis Frison, 1935:332 .

Holotype ♂ (Illinois Natural History Survey), Oregon, [Clackamas Co.], Salmon River, near Welches, Mt. Hood National Forest

Material examined. OREGON: Deschutes Co.: Deschutes River, Deschutes Bridge Campground, 11 June 2004, B. Stark, R.W. Baumann, 6♂, 8♀ ( BPS). Lincoln Co.: Siletz River, Moonshine Park, 1 June 2000, B. Stark, I. Sivec, M. Zúñiga, 6♂ ( BPS). Marion Co.: North Santiam River, Hwy 22, 3 miles above Idanhas, 3 June 2000, B. Stark, I. Sivec, M. Zúñiga, 2♂ ( BPS). Tillamook Co.: Three Rivers, Castle Rock, Hwy 22, 1 June 2000, B. Stark, I. Sivec, M. Zúñiga, 1♂ ( BPS). WASHINGTON: Clallam Co.: Soleduck River, Hwy 101, 18 June 1967, R.W. Baumann, 1♂, 3♀ ( MLBM). Skamania Co.: Wind River, Paradise Creek Campground, Hwy 30, 14 June 2004, B. Stark, R.W. Baumann, 4♂, 4♀ ( BPS).

Male epiproct. Dorsal length ca. 505-510 µm, basal width ca. 395-409 µm, width at subapical constriction point ca. 256-263 µm. Somewhat spatulate in shape, broad at base ( Figs. 1-2 ), dorsoventrally flattened, with slightly depressed concavity on dorsal surface, constricted beyond midlength, and usually broadly rounded or upturned at tip. Dorsal surface, except for narrow rim, bearing dense pile of short, setae ( Figs. 3-4 ); setae appear comb-like with several filaments arising in a common grouping; ventral surface glabrous, at least near tip.

Dorsal process. Located on tergum 9. Total width ca. 300-341 µm, median notch ca. 88-93 µm wide. Process bilobed, lateral lobes truncate to slightly rounded, each ca. 105-124 µm wide, extending above a median U-shaped notch. Dorsal surface smooth on anterior margin but eroded posteriorly ( Figs. 5-6 ).

Comments. Frison (1935) mentioned the spatulate shape of the epiproct and the mesal cleft of the dorsal process and both Ricker (1943) and Jewett (1959) used the dorsal concavity on the epiproct as an important key character for this species. In their key to Sweltsa species , Stewart & Oswood (2006) note the epiproct shape is broadest basally and upturned and broadly rounded at the tip. The only previous original figures for the epiproct of this species are those in Frison (1935) and Stewart & Oswood (2006); those in Frison (1935) were reproduced in Jewett (1959). Additional comments given below compare this species with S. pacifica .

Figures

Figs. 1-6. Sweltsa oregonensis. 1. Epiproct, dorsal aspect. 2. Epiproct, dorsal aspect. 3. Epiproct apex, dorsal aspect. 4. Epiproct surface detail. 5. Process of tergum 9, dorsal aspect. 6. Process of tergum 9, anterior aspect. (Figs. 1, 3, 4, 5 = Oregon, Deschutes Co., Deschutes River; Figs. 2, 6 = Oregon, Lincoln Co., Siletz River).