Isoperla acula Jewett

(Figs. 1 a-d)

Isoperla acula Jewett 1962 .

Holotype ♂, California, Fresno County, Dry Creek, 7 mi NE Academy.

Male. Aedeagus: sclerotized posterior process absent; body a long recurved tube without major lobes, tapering to a multi-lobed apex (Fig. 1a); a pair of long, nearly parallel patches of fine spinulae along posteroapical margin (Figs. 1 a-b). Ninth tergum with mesoposterior bipartite to oval patches of stout dark spinulae and long fine scattered setae, tenth tergum with only a few small spinulae (Fig. 1c). Posterolateral margins of at least abdominal segment 8 with scale-like setae clustered in brushes of several setae (Fig. 1d inset). Paraprocts: curved dorsally, length if straightened longer than combined first and second cercal segments, tapering gradually to long sharp apices (Fig. 1c). Vesicle: rectangular, length half as long as wide (Fig. 1d).

The male of I. acula ( I. quinquepunctata complex) is most similar to I. mormona and I. quinquepunctata, all lacking an aedeagal sclerotized process (Table 1). However, the similarity in other male taxonomic characters of the three species varies with I. acula and I. mormona possessing patches of fine spinulae near the apex of aedeagus; vesicle shape varies from lobelike ( I. quinquepunctata) to rectangular ( I. acula) and trapezoidal ( I. mormona); abdominal terga 9-10 variable posteriorly with patches of stout setae ( I. quinquepunctata) or patches of stout spinulae and scattered long setae ( I. acula, I. mormona); paraproct length> than first and second cercal segments ( I. acula) or subequal to first and second cercal segments ( I. mormona, I. quinquepunctata); and paraproct shape variable, tapering gradually to sharp apices ( I. acula), tapering abruptly to blunt apices ( I. mormona) and in I. quinquepunctata, tapering gradually to blunt apices. The current study I. acula description agrees with those of Jewett (1962), Szczytko & Stewart (1979), and Bottorff et al. (1990).

Additional Material Examined. CALIFORNIA, Shasta Co., Rock Creek, West Redding, 05/ VI /2011, larvae, (ABLC).