Isoperla umpqua Szczytko & Stewart

(Figs. 18 a-d)

Isoperla muir Szczytko & Stewart 2004 . Nomen nudum.

Isoperla umpqua Szczytko & Stewart 2013 . Holotype ♂, Oregon, Douglas County, Muir Creek, Hwy 230, downstream from bridge .

Male. Aedeagus: sclerotized posterior process present; body with one large dorsoanterior lobe (Fig. 18a); sclerotized process length approximately 0.5 mm, recurved and rod-like, with parallel lateral margins, apex clavate, and distal margin rounded in lateral and posterior views (Figs. 18 a-c). Mesoposterior area of eighth and ninth terga with bipartite patches of short stout spinulae and long fine scattered setae (Fig. 18c). 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 combined first and second cercal segments, tapering gradually to long blunt apices (Fig. 18c). Vesicle: pedunculate, length subequal to width, constricted near base with curved lateral margins, wider and rounded at apex (Fig. 18d).

Based upon the presence of a sclerotized posterior process, absence of distinct aedeagal spinule patches, and pedunculate vesicle shape, I. umpqua is placed within the I. sordida complex (Table 1). It differs from all other I. sordida complex species by possessing short stout spinulae arranged in bipartite patches along mesoposterior margins of terga 8-9. The clavate sclerotized posterior process is most similar to I. adunca; however its length is approximately twice as long as I. umpqua . Isoperla umpqua is known only from Oregon, and similar to I. baumanni, is from a single location.