Isoperla marmorata (Needham & Claassen)

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 : 49

Isoperla marmorata (Needham & Claassen)

( Figs. 8 a-d, 20 c)

Clioperla marmorata Needham & Claassen 1925 .

Holotype ♀, Nevada.

Male. Aedeagus: sclerotized posterior process present; body with one small posterior lobe, one dorsal lobe and an anterior lobe ( Fig. 8a ); one small patch of spinulae concentrated on the inverted membrane above sclerotized process ( Figs. 8 a-b); sclerotized process approaching 0.5 mm when fully extended, blade-like in lateral view ( Fig. 8a ), distal margin thin in posterior view ( Fig. 8b ), and narrow proximal portion of sclerotized process usually inverted inside posterior aedeagal membrane. 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 long blunt apices ( Fig. 8c ). Vesicle: rounded lobe, widest at base with broadly rounded apical margin ( Fig. 8d ).

The aedeagus of I. marmorata is more similar to I. fulva than to I. roguensis with similar numbers of spinule patches, patch shapes and positions. The I. marmorata aedeagus possesses two anteroapical small areas of inverted membrane which form the bases of the internal tube-like structures. Additionally, a pair of very small holes is present on the dorsal surface, usually on a minute lobe (not visible in Figs. 8a & 8c ). The pairs of inverted membrane areas and minute holes occasionally have fixed streaming seminal fluid still attached.

The previous I. marmorata aedeagal description did not include extended apical tube-like lobes ( Szczytko and Stewart 1979, fig. 123). After clearing the everted aedeagus in KOH, a pair of inverted tube-like processes were observed within the aedeagus and attached to the small inverted areas (openings) upon the anteroapical margin ( Fig. 20c ). It is possible that the previous description was based upon a live everted male that was not cleared.

Isoperla marmorata wing and body color varies significantly in California. Typically at lower elevations and into the foothills, abdominal coloration is mostly yellow (reddish-yellow in life) and hindwing anal areas are lightly tinted. An exception occurs at Butte Creek (near Chico) where both wings are completely tinted and males have a dark wide ventral band on the ninth sternum. At a higher elevation Big Chico Creek location (Tehama Co.), the abdomen is yellow with multiple brown markings and dark wings. An extreme adult phenotype of this species is found at Prairie Creek (Humboldt Co.) where the abdomen is almost completely brown and the wings nearly black (J.J. Lee, pers. com.).

Additional Material Examined. CALIFORNIA, Siskiyou Co., McCloud River, Hwy 89 Lower Falls Picnic Area 5.5 (8.8 km) mi E McCloud, 41.2402°N, 122.02441°W, 23/ V /2013, J.B. Sandberg, B.C. Kondratieff, 3♂, 1♀ ( JBSC) . OREGON, Lake Co., Deep Creek, Hwy 140, 5.5 mi (8.8 km) E Adel, 42.18564°N, 119.99512°W, 20/ V /2013, J.B. Sandberg, B.C. Kondratieff, 4♂, 2♀ ( JBSC) .

Figures

Figs. 7-8. Adult male characters of Isoperla laucki, Dragsaw Spring, Humboldt Co., CA, and I. marmorata, Big Chico Cr., Tehama Co., CA, 32-40x. Fig. 7a. I. laucki aedeagus, lateral; sclerotized process (white arrow & inset-lateral view); posteroapical and posterobasal spinule patches (black arrows). Lobes A: posterior, B: dorsal, C: anterolateral pair. Fig.7b. Aedeagus, ventral; sclerotized process (white arrow & inset-dorsal view); posterobasal spinule patch (black arrow). Fig. 7c. Paraprocts (left white arrow); sclerotized process (right white arrow); posteroapical spinule patch (black arrow). Fig. 7d. Vesicle. Fig. 8a. I. marmorata aedeagus, lateral; sclerotized process (white arrow & inset-lateral view); paraprocts (black arrow). Lobes A: posterior, B: dorsal, C: anterior. Fig. 8b. Aedeagus, posterior; spinule patch & sclerotized process (black arrow). Fig. 8c. Paraprocts (arrow). Fig. 8d. Vesicle.

Figs. 20a-f. The cleared aedeagus of six western Nearctic Isoperla species after live evertion; membranous opening of internal tube like process or apex (white arrows); tube like internal process (black arrows). 50x (20b, d & e, cropped and enlarged). 20a. I. baumanni, lateral view, partially everted; 20b. I. fulva, lateral view; 20c. I. marmorata, lateral view; 20d. I. miwok, dorsoapical view, tube like process openings along anteroapical margin; 20e. I. roguensis, ventral view, tube like process openings along anteroapical margin; 20f. I. tilasqua, lateral view.