Sweltsa pacifica (Banks)

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 : 250-252

Sweltsa pacifica (Banks)

( Figs. 7-12 )

Chloroperla pacifica Banks, 1895:313 .

Holotype ♀ (Museum of Comparative Zoology), Washington, Skokomish River

Alloperla spatulata Needham & Claassen, 1925:120 . Holotype ♂ (Cornell University), California, San Antonio Canyon near Claremont, Synonymy by Ricker, 1952:182

Material examined. CALIFORNIA: Calaveras Co., Jesus Maria Creek, near North Calaveras River , Mokelumne Hill , 7 May 1987, R . Bottorff, A. Knight, 1♂, 1♀ (RB). Nevada Co., Prosser Creek, Hwy 89, 24 June 2009, B. Stark, C. R. Nelson, K. Nye, A. Harrison, 2♂, 3♀ ( BPS). Placer Co.: Truckee River, Hwy 89, 1 mile south of Truckee , 19 June 1985, R.W. Baumann, C. R. Nelson, M. Whiting, 15♂, 15♀ ( MLBM). Truckee River, Hwy 89, Goose Meadow Campground , 22 June 2009, B. Stark, K. Nye, A. Harrison, 14♂, 7♀ ( BPS). Plumas Co.: Little Last Chance Creek , above Chilcoot Campground , 7 June 2004, B. Stark, R. W. Baumann, 2♂, 4♀ ( BPS). Riverside Co.: Stone Creek, below Pine Cove , San Jacinto Mountains , 21 June 1977, R. W. Baumann, C. Hogue, 1♂, 3♀ ( MLBM). Sierra Co.: Little Truckee River, Hwy 89, 14 mi north of Truckee , 21 June 2009, B. Stark, K. Nye, A. Harrison, 1♂ ( BPS) . OREGON: Lincoln Co.: Siletz River, Moonshine Park , 1 June 2000, B. Stark, I. Sivec, M. Zúñiga, 1♂ ( BPS) . WASHINGTON: Chelan Co.: seep at Nason Creek, above White Pine Campground , 16 June 2004, B. Stark, R . W. Baumann, 2♂, 2♀ ( BPS) .

Male epiproct. Dorsal length ca. 490-530 µm, basal width ca. 137-157 µm, greatest width ca. 235-265 µm. Epiproct dorsoventrally flattened, broad basally becoming gradually wider, then abruptly widened into subtriangular apex terminating in small nipplelike point ( Figs. 7-10 ); dorsum concave, apex slightly upturned. Dorsal surface bearing dense pile of short, multifilament setae except for glabrous margin around subapical triangular region ( Figs. 10-11 ); ventral surface glabrous.

Dorsal process. Located on tergum 8, some specimens bear slightly elevated ridge on tergum 9. Total width ca. 90-120 µm, median notch shallow, V-shaped. Process broad basally, lateral margins angled sharply to apex of projections ( Fig. 12 ).

Comments. Banks (1895) original description of this species is based primarily on pigment pattern and wing venation, no figures are given. Needham & Claassen (1925) include the first figures of the male (Plate 22, Fig. 2 ) and provide a figure of the male Alloperla spatulata (Plate 21, Fig. 14 ), now considered a synonym of S. pacifica . The latter figure shows the dorsal aspect of the epiproct much more accurately than does the former, but other authors (e.g. Jewett 1959) have selected the less accurate figures for reproduction. Stewart & Oswood (2006) study prepared new figures which show the two dorsal processes, however the epiproct shape in their Fig. 7.94 shows a constriction not found in our specimens. One reviewer checked additional S. pacifica specimens from California, Oregon and Washington and noted an apparent constriction for specimens in which the epiproct is closely appressed to the cowl, however, on closer inspection, no actual constriction occurred in these specimens. Specimens from the Stewart & Oswood (2006) should be re-examined for the presence of this epiproct feature.

The broad and dorsoventrally flattened epiproct of this species is more similar to that of S. oregonensis than to S. resima or S. townesi . However, significant differences including the presence of an apical nipple-like structure, an extensive apical glabrous area, and the absence of a mesal constriction in our S. pacifica specimens, suggest S. oregonensis and S. pacifica are not so closely related as to be placed together in a single species group.

Figures

Figs. 7-12. Sweltsa pacifica. 7. Epiproct, dorsal aspect. 8. Epiproct, dorsal aspect. 9. Epiproct apex, anterior aspect. 10. Epiproct apex, dorsal aspect. 11. Epiproct surface detail. 12. Process of tergum 8, anterior aspect. (Figs. 7, 9, 11 = California, Sierra Co., Little Truckee River; Figs. 8, 10, 12 = California, Placer Co., Truckee River).

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).

Figs. 13-18. Sweltsa resima. 13. Epiproct, dorsal aspect. 14. Epiproct apex, dorsal aspect. 15. Epiproct, anterior aspect. 16. Epiproct, anterior aspect. 17. Epiproct surface detail. 18. Process of tergum 9, anterior aspect. (California, Inyo Co., Division Creek).