Isoperla denningi Jewett, 1955

Sandberg, John B. & Kondratieff, Boris C., 2013, The Isoperla Of California (Plecoptera: Perlodidae); Updated Male Descriptions And Adult Keys For 18 Western Nearctic Species, Illiesia 9 (5), pp. 34-64 : 46

Isoperla denningi Jewett

( Figs. 5 a-d)

Isoperla denningi Jewett 1955 .

Holotype ♂, California, Los Angeles County, 4 mi W Tanbark Flat.

Male. Aedeagus: sclerotized posterior process present; body with two posterobasal lobes, one large posteroapical lobe, and one dorsolateral pair of rounded lobes ( Fig. 5a ); sclerotized process length <0.5 mm, recurved and rod-like, apex clavate in lateral view ( Fig. 5a ), bifurcate in posterior view, lateral apices short and rounded ( Fig. 5b ), and width of expanded apicolateral lobes 0.09-0.10 mm. 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 combined first and second cercal segments, tapering gradually to blunt apices ( Fig. 5c ). Vesicle: pedunculate, length subequal to width, constricted near base with curved lateral margins, wider and rounded at apex ( Fig. 5d ).

Isoperla denningi is common in southwestern California, from Santa Barbara County south to San Diego County and occasionally coexists with I. acula , I. adunca and I. mormona ( Sandberg 2011b) . It is most similar to the species in the I. sordida complex, specifically I. sordida Banks 1906 ( Table 1 ), with discernible differences in aedeagal characters. Both species have four aedeagal lobes in lateral view, however I. denningi has a pair of dorsal lobes and I. sordida has only one. The sclerotized processes are somewhat similar; both are slightly bifurcate with short rounded apices. The difference is the plane in which these apices lie: for I. sordida , the apical plane is perpendicular to the body of the process, and for I. denningi , the apical plane is parallel with the sclerotized process body. Additionally, the widths of the bifurcate apices differ: 0.09-1.0 mm for I. denningi and 0.18-0.20 mm for I. sordida .

Additional Material Examined. CALIFORNIA, Riverside Co., San Juan Creek, 0.4 mi (0.6 km) N Lion Canyon Creek , 19/ V /2011, larvae ( ABLC); San Diego Co., Devils Canyon Creek, above San Mateo Canyon Creek , 16/ V /2011, larvae ( ABLC); King Creek, 1.1 mi (1.77 km) below Grove Drive , 30/ V /2012, larvae ( ABLC); Santa Ysebel Creek, 2 mi (3.2 km) S Dan Price Creek , 29/ V /2011, larvae ( ABLC); Juaquapin Creek, above Sweetwater River , 01/ VI /2011, larvae ( ABLC).

Figures

Figs. 5-6. Adult male characters of Isoperla denningi, San Mateo Cr., San Diego Co., CA, and I. fulva, Sand Cr., Larimer Co., CO & Pole Cr., Juab Co., UT, 32-50x. Fig. 5a. I. denningi aedeagus, lateral; sclerotized process (arrow & inset-lateral view). Lobes A-B: posterobasal, C: posteroapical, D: dorsolateral pair. Fig. 5b. Aedeagus, ventral; sclerotized process (arrow & inset-posterior view). Fig. 5c. Paraprocts (arrow). Fig. 5d. Vesicle. Fig. 6a. I.fulva aedeagus, lateral; sclerotized process (left white arrow & inset-lateral view); spinule patch (right white arrow & inset); paraprocts (inset-black arrow). Lobes A: posterior, B: dorsal, C: anterior. Fig. 6b. Aedeagus, ventral; sclerotized process (arrow & inset-posterior view). Fig. 6c. Aedeagus, dorsal; sclerotized process (black arrow); spinule patch (white arrow). Fig. 6d. Vesicle.