Isoperla tilasqua Szczytko & Stewart

(Figs. 17 a-d, 20f)

Isoperla tilasqua Szczytko & Stewart 1979 .

Holotype ♂, Oregon, Benton County, Oak Creek.

Male. Aedeagus: sclerotized posterior process absent; body with two large posterior lobes and expanded apex, apex deeply inverted, with a pair of small conical lobes at apicolateral margins (Fig. 17a); one large patch of spinulae concentrated below posteromedian lobe (Fig. 17b), and a long thin patch along posteroapical margin (Fig. 17c). Abdominal terga 8-9, 9, 9-10: without stout spinulae or long stout setae. Posterolateral margins of at least abdominal segment 8 with scale-like setae clustered in brushes of several setae. Paraprocts: curved dorsally, length if straightened subequal to first cercal segment, tapering abruptly to blunt apices (Fig. 17c). Vesicle: rounded lobe, widest at base with broadly rounded apical margin (Fig. 17d).

Isoperla tilasqua is not known from California, recorded from Oregon and Washington (Szczytko & Stewart 1979, Sandberg 2011b) and is most similar to I. baumanni . See comments under I. baumanni .

After live eversion, the extended tube-like lobes described in Szczytko & Stewart (1979, fig. 116) remained inverted, their locations could be identified by small inverted membrane areas (openings). After clearing in KOH, a pair of tube-like internal processes was discernible within the body of the aedeagus, with openings along the anteroapical margin (Fig. 20f).

Additional Material Examined. OREGON, Harney Co., Trout Creek, NFD 395 Rd 4.25 mi (6.8 km) E Idlewild CG ( Hwy 395), 43.80484°N, 118.91082°W, 21/ V /2013, J.B. Sandberg, B.C. Kondratieff, 4 Larvae, 2♂, 3♀ (reared) (JBSC); Umatilla Co., Camas Creek, Hwy 395 Ukiah-Dale Forest State Park 1.1 mi (1.8 km) S Hwy 244 intersec, 45.1241°N, 118.97251°W, 22/ V /2013, J.B. Sandberg, B.C. Kondratieff, 2♂, 1♀ (JBSC).