Hesperoperla pacifica (Banks)

Stark, Bill P. & Green, Stephen, 2011, Eggs Of Western Nearctic Acroneuriinae (Plecoptera: Perlidae), Illiesia 7 (17), pp. 157-166 : 162-163

Hesperoperla pacifica (Banks)

( Figs. 21-30 )

Acroneuria pacifica Banks, 1900:242 .

Holotype ♀ (Museum of Comparative Zoology), Olympia [Thurston Co.], Washington

Material examined. Alberta: Battle Creek at Reservoir Lake, 23 June 1975, L. Dosdall, 1♀ ( BPS). California: Humboldt Co., East Fork Willow Creek, Hwy 299, 24 April 1987, B. Stark, R.W. Baumann, C. R. Nelson, 2♀ ( BPS). Shasta Co., North Fork Battle Creek, south of Shingletown, 8 June 2004, B. Stark, R.W. Baumann, 1♀ ( BPS). Tehama Co., North Fork Battle Creek, Wildcat Road, 26 April 1987, B. Stark, R.W. Baumann, C. R. Nelson, 2♀ ( BPS). Colorado: Gunnison Co., Gunnison River, Hwy 135, 8 June 2003, B. Stark, 3♂, 2♀ ( BPS). Idaho: Bonneville Co., Snake River, 4 July 1972, G. Tourtlotte, 1♂, 1♀ ( BPS). Fremont Co., Big Springs, 5 miles east Macks Inn, 25 July 1979, B. Stark, K.W. Stewart, R.W. Baumann, 4♀ ( BPS). Montana: Carbon Co., East Rosebud River, Roscoe, 23 July 1989, B. Stark, 5♂, 3♀ ( BPS). Lewis & Clark Co., Trout Creek, Vigilante Campground, 21 August 2004, B. Stark, I. Sivec, 1♂, 1♀ ( BPS). New Mexico: San Miguel Co., Pecos River, 6 miles north Pecos, 12 July 1973, B. Stark, 2♂, 3♀ ( BPS). Nevada: Elko Co., Secret Creek, Secret Pass, 15 June 1974, B. Stark, 1♂, 1♀ ( BPS). Oregon: Jefferson Co., Metolius River at headwater spring source, 11 July 1979, B. Stark, K.W. Stewart, 5♂, 3♀ ( BPS). Tillamook Co., Nehalem River at Cronin Creek jct., 4 June 1991, B. Stark, R.W. Baumann, C. Henderson, 1♀ ( BPS). Wyoming: Park Co., Clarks Fork Yellowstone River, below Cooke City, 20 July 1989, B. Stark, 3♂, 1♀ ( BPS). Egg. Outline oval with short, wide collar ( Fig. 21 ); collar base encircled by a prominent basal ring, ca. 137-176 μm wide ( Figs. 23 , 25, 27, 29 ); sides of egg body along basal ring bearing a series of vertical ridges separated by wide depressions. Egg length ca. 428-484 μm, equatorial width ca. 312-324 μm, collar length ca. 34-55 μm, median collar width ca. 41-58 μm, rim width ca. 89-116 μm. Sides of collar with several prominent vertical ridges, rim flanged and irregularly incised. Chorionic surface appearing smooth ( Figs. 21 , 26, 28, 30 ) but with obscure hexagonal follicle cell impressions sometimes apparent at higher magnifications. Micropyles located near equator; orifices raised slightly ( Fig. 24 ). Comments. Hesperoperla eggs are generally similar to those of Calineuria californica in shape, collar form and in having a basal ridge encircling the collar base (Baumann & Stark 1980; Isobe 1997). The most conspicuous feature distinguishing the eggs of the two genera is the row of vertical struts on the egg body which connect to the basal ridge in Hesperoperla ( Fig. 25 ) which are absent in eggs of Calineuria ( Fig. 2 ). No consistent morphological differences were found among eggs of different populations of H. pacifica , or between eggs of H. hoguei and H. pacifica . However, variations are evident in the images of H. pacifica eggs from different sites ( Figs. 21-30 ), especially in shape of the anterior pole (e.g. Figs. 26, 28 ), shape of the collar (e.g. Figs. 25, 27 ) and in length of lines delimiting cells surrounding the basal ridge (= vertical struts). The specimen shown from the Gunnison River, Colorado, for example, has a few long lines of at least 57 μm ( Fig. 25 ), whereas the longest vertical struts on the specimen shown from Trout Creek, Montana ( Fig. 27 ) are only 30 μm.

Figures

Figs. 21-24. Hesperoperla pacifica eggs, Idaho, Bonneville Co., Snake River. 21. Egg, lateral aspect. 22. Egg, apical aspect. 23. Collar end. 24. Micropyles.

Figs. 25-30. Hesperoperla pacifica eggs. 25-26. Colorado, Gunnison Co., Gunnison River. 25. Collar end. 26. Anterior end. 27-28. Montana, Lewis & Clark Co., Trout Creek. 27. Collar end. 28. Anterior end. 29-30. Oregon, Jefferson Co., headwaters Metolius River. 29. Collar end. 30. Anterior end.

Figs. 1-4. Calineuria californica eggs, Montana, Lincoln Co., Yaak River. 1. Egg, lateral aspect. 2. Collar end. 3. Collar end with anchor. 4. Anterior end.