Isoperla karuk, Baumann & Lee, 2009

Baumann, Richard W. & Lee, Jonathan J., 2009, Two Interesting New Species Of Isoperla From Northern California (Plecoptera: Perlodidae), Illiesia 5 (1), pp. 1-10 : 5-9

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Isoperla karuk


Isoperla karuk sp.n.

( Figs. 17‐32 View Figs View Figs )

Material examined. Holotype ♂ from California , Humboldt County, Klamath River @ junction of Aikens Creek, 29‐III‐06, J.J. Lee . Paratypes (J. J. Lee, collector): ‐ California , Humboldt Co., same data as holotype, 29‐III‐06, 2 ♂ ; 27‐II‐08, 1 ♂; 6‐III‐08, 1 ♀; Mad River @ Mad River Fish Hatchery, 19‐IV‐06, 2 ♂, 3 ♀ ; 7‐IV‐07 2 ♂; 18‐IV‐07, 1 ♂, 1 ♀; 19‐IV‐07, 6 ♂; 5‐V‐07, 1 ♂; 8‐IV‐08, 1 ♀; 12‐V‐08, 1 ♀; Mad River @ 1 st curve Mad River Rd., 20‐III‐06, 1 ♂ ; 29,30‐III‐07, 12 ♂, 10 ♀; 1‐IV‐07, 2 ♂, 1 ♀; 3‐IV‐07, 3 ♂, 1 ♀; 4‐IV‐ 07, 1 ♀ (reared); 7‐IV‐07, 4 ♂; 28‐IV‐07, 1 ♂; 17‐III‐08, 1 ♂. Holotype deposited at the California Academy of Sciences .

Male. Macropterous. Length of forewings 8.5‐10.5 mm; length of body 8.0‐9.0 mm. General body color medium brown. Head with ocelli and base of antennae connected by dark brown M‐ shaped pigment band; yellow patch forward of anterior ocellus and between lateral ocelli and compound eye; interocellar space ranging from mostly yellow to an oval, central yellow spot; occiput light brown, with lateral light oval patch broken by brown reticulations, light patch broadly to barely connected to yellow patch adjacent to eyes; antennae brown. Pronotum with wide, median light stripe; disks light brown to lateral margins, rugosities darker brown; anterior and posterior margins cream to light brown. Meso and metanota dark brown, large yellow patch anteriorly between mesonotal wing bases. Wings hyaline, veins brown, fumose in coastal space. Legs light brown, femur with proximal dorsal brown mark and longitudinal dorsal brown stripe, tibia with incomplete narrow brown band in proximal onefourth. Abdominal terga medium brown dorsally, pale laterally, a pair of median light marks on first few terga, broken brown stripes appearing weakly laterally; abdominal sterna cream colored with brown marks at pleural folds, medial and mediolateral pair of brown spots evident to varying degrees. Vesicle short, broadly rounded ( Fig. 29 View Figs ). Cerci brown, segments with one long posteroventral seta. Paraprocts short and stout, apically pointed, barely curving over tenth tergum ( Fig. 30 View Figs ). Aedeagus ( Figs. 17 & 19 View Figs ) with a large posteromedial bihemispherical lobe bearing long, rust colored anteriorly directed spinules ( Figs. 18 View Figs & 25 View Figs ); a thin, sclerotized, clavate process (lateral view), projecting from midventral margin of bi‐ hemispherical lobe, keeled dorsally and ventrally, flattening apically, heavily sculptured and spinulate ( Figs. 21‐24 View Figs ); a pair of lobes positioned laterally on either side of bihemispherical lobe, bearing rust colored spinules directed posteriorly ( Figs.17, 20 View Figs & 26 View Figs ); a patch of thin light colored spinules located below clavate process, narrowed and fringed apically ( Figs. 22 View Figs & 27 View Figs ). A band of small, light brown spinules encircling base, with areas projecting forward laterally, spinules short and rounded at apex, each with a lateral hair‐ like process ( Figs. 19 View Figs & 28 View Figs ); anterior surface of aedeagus void of spinules ( Figs. 17 & 19 View Figs ).

Female. Macropterous. Length of forewings 10.0‐ 10.5 mm; length of body 9.0‐10.0 mm. General body color and head and pronotal pigmentation patterns similar to male. Subgenital plate brown, darker than rest of segment, triangular, terminating in broad triangular point, produced ¼ to ½ over length of sternum 9.

Egg. Shape oval, round in cross section, narrower toward poles ( Fig. 31 View Figs ). Collar well developed, higher and with broader flanges ( Fig. 32 View Figs ) than shown for I. fulva and I. marmorata in Szczytko & Stewart (1979). Chorion with thickened ridges, forming pentagon shaped depressions, proteinaceous bodies sometimes present. Micropyles appearing on the bottom half of the egg. Color dark brown and opaque.

Larva. Unknown.

Etymology. The species name is a noun in apposition and honors the Karuk people of the Klamath River in northern California. The common name Klamath Stripetail is suggested.

Diagnosis. Isoperla karuk is placed in the Isoperla marmorata complex which includes I. marmorata (Needham and Claassen) and I. fulva Claassen. It shares the following characteristics ( Szczytko & Stewart 1979): 1. male aedeagus bearing a spinose, club‐ shaped, sclerotized process; 2. broadly rounded, shallow male vesicle; 3. angulate female subgenital plate (shared with I. fulva ). The male is easily distinguished from other members of the complex by the unique aedeagus with a bi‐ hemispherical lobe bearing reddish brown spinulae directed anteriorly and two smaller lobes bearing reddish brown spinulae directed posteriorly. The I. karuk female cannot presently be distinguished from the female of I. fulva by the shape of the subgenital plate but the egg has a higher and more broadened collar. Nymphs that we believe are I. karuk fit the description for I. marmorata ( Szczytko & Stewart 1979) .

Remarks. This species was collected from medium sized rivers close to sea level. Adults were found from February into May. The peak I. karuk emergence period, on the Mad River, followed the peak emergence of I. pinta Frison and preceded the peak I. mormona Banks emergence period. The riverine habitat made benthic collection of nymphs problematic. Several nymphs were collected, however, and three reared nymphs turned out to be three separate Isoperla species ( I. karuk , I. mormona and I. marmorata ?). Field caught females and males were maintained together in order to obtain mature ova. Females were alive after 43 days and appeared to feed on, or at least consume the juice of apple slices.

Since this species is difficult to separate from I. fulva in both the male and female adult stages without extruding the aedeagus or studying the eggs, the identity of specimens previously listed as I. fulva from California is questionable. Jewett (1960) in his study of the California stonefly fauna listed two records for I. fulva : one in El Dorado County and one in Modoc County. Later, Szczytko & Stewart (1979) listed two additional records: Plumas County and Modoc County (Oregon).