Isoperla baumanni Szczytko & Stewart, 1984

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 : 43

Isoperla baumanni Szczytko & Stewart

( Figs. 3 a-d, 20 a)

Isoperla baumanni Szczytko & Stewart 1984 .

Holotype ♂, California, Plumas County, Domingo Spring, Domingo Spring Campground , 6 mi NW Chester.

Male. Aedeagus: sclerotized posterior process absent; body with one posterobasal lobe, one posteromedian lobe and expanded apex, apex deeply inverted ( Fig. 3a ); one large patch of spinulae concentrated below posteromedian lobe ( Fig. 3b ), and a long thin patch along posteroapical margin ( Fig. 3c ). 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. 3c ). Vesicle: rounded lobe, widest at base with broadly rounded apical margin ( Fig. 3d ).

The males of I. baumanni and I. tilasqua are very similar, with the exception of recently preserved specimens. Males of I. baumanni have yellow abdominal pigmentation which can be easily separated from the much darker I. tilasqua . The aedeagal spinulae and lobe characters are very similar; both species possess one large patch of spinulae concentrated below the posteromedian lobe, a long thin patch along posteroapical margin, and bulbous apex deeply inverted ( Figs. 3 a-c, 17a-c). Isoperla tilasqua differs slightly from I. baumanni (live everted) by usually possessing a pair of small apicolateral lobes (similar to I. sobria ( Hagen 1874)) . Males of both species may be identified using the thin extended apical lobe characters illustrated in Szczytko & Stewart (1979, fig. 116; 1984, fig. 53); I. baumanni has only one extended tube-like lobe and I. tilasqua has two. Sandberg (2011b) suggested that extended lobes are normally inverted internal structures, and evert only when using the KOH clearing-eversion method for preserved males ( Szczytko & Stewart 1979). These lobes could not be everted using the live eversion, hot water fixing, and KOH clearing methods described in this study.

The aedeagi of live everted I. baumanni and I. tilasqua were cleared in KOH to detect the inverted tube-like processes. The internal membrane of a single inverted apical process was visible inside the aedeagus of I. baumanni after clearing ( Fig. 20a ). The apical inverted process could only be partially everted for I. baumanni , with the longitudinally striated apex remaining inverted. For I. tilasqua , a pair of inverted tube-like processes could be observed within the aedeagus, but could not be everted after clearing ( Fig. 20f ).

The I. baumanni aedeagal shape, stout spinule patches, paraproct and vesicle shape are also similar to I. gravitans ( Needham & Claassen 1925) in Szczytko & Stewart (1979, figs. 106-110). Sandberg (2011b) also had difficulty separating I. baumanni from I. tilasqua nymphs using lacinia characters and tentatively placed I. baumanni into the I. sobria species complex. The three species appear to have locally restricted distributions and further study will be necessary to understand species limits of I. baumanni , I. tilasqua , and I. gravitans .

Figures

Figs. 3-4. Adult male characters of Isoperla baumanni, Domingo Springs, Plumas Co., CA and I.bifurcata, Mosquito Spring, Plumas Co., CA, 25-50x. Fig. 3a. I. baumanni aedeagus, lateral; large posterobasal spinule patch & thin apical patch (arrows). Lobes A: posterobasal, B: posteromedian. Fig. 3b. Aedeagus, posterior; large basal spinule patch (arrow).Fig. 3c. Paraproct (white arrow); apical thin spinule patch (black arrow). Fig. 3d. Vesicle. Fig. 4a. I. bifurcata aedeagus, lateral. Lobes A: posterobasal, B: posteromedian, C: dorsal, D: anterior lobe.Sclerotized process characters 1: base, 2: median arm, 3: bifurcate arms, 4: subapical barb & apical tine. Fig. 4b. Aedeagus, ventral. Fig. 4c. Paraproct (arrow). Fig. 4d. 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.